Prince Harry and Meghan Markle have been warned they could 'upstage' the Coronation if they try to go big on Archie's birthday celebration.
The royals are said to be still considering the invitation to attend the ceremony in ten weeks' time.
The event clashed with their son Archie's fourth birthday, but they are determined to still mark the day even if they jet back to Britain.
If they are to return in early May, insiders say they still intend to throw a party for their son - just like they would have done in California.
But they have been told they risk overshadowing Harry's father's big moment, Express.co.uk report.
That includes the release of a birthday announcement hours before the coronation.
The couple celebrated Lilibet Diana's birthday during the Queen's Platinum Jubilee last summer and went on to release a portrait of her.
Royal columnist Lee Cohen says the weekend must only be about one thing.
He said: "It's terribly petty, but the Sussexes, who no longer have their royal platform, seem to relish any opportunity to attempt to upstage a royal occasion.
"It's not as if the Royal Family seek occasions to upstage the antics of the Sussexes, quite the opposite."
Royal correspondent Natalie Oliveri says if Harry and Meghan are to attend they can take no risks.
She said: "They're being encouraged to not pull any stunts during the coronation and really stick to the plan.
"I think their appearance at the coronation will be very similar to that of the Queen's Platinum Jubilee last year.
"We might see them at one or two events but largely they will be kept in the shadows because they don't want to take away from the historical event.
"It's also Archie's birthday too so they might host a little party at Frogmore Cottage like they did with Lilibet."
Harry and Meghan have still not decided whether they are flying to the UK for the occasion despite being invited as part of the 2,000-strong congregation at Westminster Abbey.
According to sources, whether Harry and Meghan attend rests on one simple demand.
It is understood Harry wants a summit with King Charles and Prince William to discuss their issues before committing to come.
But the Duke and Duchess attending the Coronation would "ruin it" for King Charles, another royal commentator claims.
Author Tom Bower said the monarch is a "weak man" who worries about Harry and suggested their attendance could be too much for him
Speaking to GB News, he claimed"people were "sick" of the Sussexes and would prefer them to stay at home for the momentous occasion.
Mr Bower said: "His problem is that he is a weak man in a way and he's worried about Harry.
"If only he said to Harry, look, come to the Coronation, but you can have row Q, seat 54 and viewers partly obscured by a column, then the message will get through.
"But I think if he allows Harry to come to the Coronation, it is going to ruin the Coronation. It'll be overshadowed by Harry's presence and Meghan's too.
