Monday’s gathering – being described as the “Sandringham summit” – will see her meet the Prince of Wales, the Duke of Cambridge and Prince Harry, while Meghan is expected to join over the phone from Canada, as they weigh up what Buckingham Palace calls “complicated issues”.
But what questions will they have to consider?
Will their existing funding be cut?
The couple say they want to become “financially independent”.
They have proposed giving up the Sovereign Grant, paid annually by the government to support the Royal Family in its official duties.
The duke and duchess say it currently accounts for about 5% of their current staff costs, which they will need to find elsewhere.
Their remaining costs come from income produced by the Duchy of Cornwall, Prince Charles’ £1bn estate. Statements on the Sussexes’ website suggest the couple expect this will continue.
They say they already pay the costs of their private travel.
After criticism of their use of private jets last year, they say that wherever possible this will be by “commercial air carriers, local trains and fuel-efficient vehicles”.
Official visits are carried out at the request of the Foreign Office and are paid out of the Sovereign Grant – and it seems that the duke and duchess anticipate that this will not change.
How will they earn money?
By most people’s standards Prince Harry and Meghan are already very wealthy.
David McClure, author of Royal Legacy, a book about the Royal Family’s finances, says the duke inherited £7m when his mother died, while Meghan was a successful actress when they met.
“Together, they might well be worth £10m to 15m,” he says.
But the couple could turn to the private sector to earn more money. Mr McClure says senior royals are aware that working in the commercial sector can be a “potential minefield”.
And BBC royal correspondent Jonny Dymond says the general rule has always been that if you are a working royal, you don’t really do paid work, especially if it could cause a conflict of interest.
The Earl and Countess of Wessex faced such allegations when they tried to run a TV company and PR firm, respectively.
Nearly any employment they might embark on would open the duke and duchess up to criticism that they were exploiting or monetising the royal brand, our correspondent adds.
Will they keep their royal titles?
There has been no indication that the duke and duchess intend to renounce their titles.
When Archie was born, his parents decided that he would have no title – he is simply Archie Harrison Mountbatten-Windsor.
Harry’s mother, Princess Diana, gave up the title “Her Royal Highness” when she divorced Prince Charles. However, commentators have suggested the Palace is unlikely to go down this road again given the criticism it faced following this move.
In December it was also revealed that the couple had made an application to trademark their Sussex Royal brand across a string of items including books, calendars, clothing and charitable fundraising – and renouncing their royal titles could mean they lose some of the status this brand is built on.
The meeting is unlikely to consider the issue of succession: it would take an act of Parliament to alter the line of succession, where Prince Harry currently stands in sixth place.
Where will they live?
The proposal from the duke and duchess is that they divide their time between the UK and North America.
Canada, where the couple spent a six-week break over Christmas, has been touted as a possible base for the couple. Meghan lived and worked in Toronto for seven years during her time starring in the US legal drama Suits and has several Canadian friends.
The Daily Mail’s royal correspondent, Rebecca English, has suggested the couple may eventually settle in Los Angeles, the city where she grew up and her mother still lives – but not until President Trump’s time in the White House is over.
How much time they spend in the UK may be a crucial question, as Meghan is believed to be applying to be a British citizen, which requires that she only spends 90 days abroad each year.
And as Archie – currently only eight months old – grows up, where he attends school could determine where the duke and duchess have their main home.
Will they keep Frogmore Cottage?
The couple plan to continue to use the Grade II-listed house in Windsor, which was refurbished with £2.4m in taxpayer funds.
Keeping it will ensure they “will always have a place to call home in the United Kingdom”, they said.
But they acknowledge that this depends on the permission of the Queen, who owns the property.
How will they conduct their tax affairs?
If the couple choose to base themselves outside the UK for any length of time, there are likely to be tax implications, according to BBC royal correspondent Nicholas Witchell.
Under the Canadian tax system, anyone who lives in the country for 183 days or more a year must pay tax on their global income, regardless of where it is earned or received.
Similar rules apply in the UK, but the limit is 90 days.
Harry has been warned he risks facing a “double tax” on his income if he divides his time between the two countries, according to the Mail on Sunday.
Will they still carry out royal duties?
The duke and duchess said in their statement on Wednesday that they intend to continue “to honour our duty to the Queen, the Commonwealth, and our patronages”.
One of the tasks facing the meeting of senior royals will be to decide what exactly this means.
“It’s not at all clear how much in the way of royal duties the prince and Meghan see themselves doing,” says the BBC’s Jonny Dymond.
Former Buckingham Palace press officer Dickie Arbiter said any attempt to step back from their royal duties would pose problems.
“You’re either a royal or you’re not a royal – you can’t have one leg in one camp and another leg in another camp,” he said.
According to tables compiled each year by retired insurance broker Tim O’Donovan, the duke attended 201 engagements last year – his second-highest number since he committed to full-time public duties – while the duchess had 83 engagements.
That is some way below the number of the busiest royal, Prince Charles, who attended 521 functions – although Mr Donovan stresses that the effort and preparation for each varies.
What will their foundation do?
In April, the Sussexes intend to launch a new foundation, which they say will “advance the solutions the world needs most” through “local and global community action”.
They say they have researched the work of many well-known and lesser-known foundations in developing their plan.
The Sunday Telegraph says they may try to model their foundation on organisations like those run by Barack and Michelle Obama, Bill and Melinda Gates and George and Amal Clooney.
The paper says the couple have obtained a UK trademark for The Foundation of the Duke and Duchess of Sussex.
But it says that if they want to attract wealthy US-based donors, they may also need to set up a stateside “friends of” organisation so donors can benefit from local tax-breaks.
How will they handle the media?
The Sussexes’ handling of media relations has already caused controversy within the Royal Family. A source told the BBC that Prince William was “furious” after the couple’s ITV interview in October.
With the duke and duchess proposing major changes in their PR operation, other royals will have an opportunity to raise concerns at the meeting.
Part of their plan is to withdraw from the royal rota, which gives some UK publications privileged access to royal engagements on condition that they share pictures and quotes with other publications.
The couple say they are concerned about “frequent misreporting”. They also say they want to connect with the public more directly through social media, adding that the rota system can restrict them from publishing new images themselves.
Will their security be downgraded?
The couple say their security as “internationally protected people”, provided by armed Metropolitan Police officers, is mandated by the Home Office.
Shadow foreign secretary Emily Thornberry said this arrangement should continue.
“I think the British taxpayer should pay for the security of Harry and Meghan and their family as they do for former ministers,” she told the BBC’s Andrew Marr Show, highlighting Prince Harry’s Afghanistan service.
Home Secretary Priti Patel said “safety was always a priority” for the Royal Family, although she said she would not discuss the arrangements for protected individuals.
But the Sunday Times said the Metropolitan Police is considering replacing expensive firearms officers with guards armed with Tasers for several VIPs, in order to cut costs.
It quotes former head of royal protection Dai Davies saying the move would be “nonsensical”, however, because of the Taser’s short range and one-shot limit.