Ingrid Seward predicted the whole family will reunite on Sunday – minus Prince Harry and Meghan, the Duchess of Sussex – with it being a chance for them to get together before the King’s Coronation in May.
They usually stick to traditions during the four-day holiday, eating a fish dinner on Good Friday.
On Sunday they go to St George’s Chapel for a service before heading back for a four-course roast.
But Ms Seward said Charles may relax one rule that was enforced by his late mother.
She told The Sun: “They will all have dinner together, but not the young children, they will eat in the nursery dining room.
“The Queen always said until they could hold a knife and fork properly they could not eat at the table, but Charles might have relaxed that rule a bit.”
The expert also believes Kate may have an additional role ahead of the occasion as she helps to organise some of the activities for the children.
She said: “Kate is a great organiser and will almost certainly organise an Easter egg hunt – they can also go to the royal mews and see the horses there and there is an indoor pool for swimming and ponies for them to ride.”
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During her reign, the Queen often invited members of the family to the castle for the long weekend where they could spend quality time together away from their busy lives as working royals.
Former royal chef Darren McGrady has previously shared some of the secrets from his time cooking Easter dinner for the late Queen and her relatives.
Meal times are said to be very important at the castle over Easter weekend.
On Friday, the family will have a traditional fish dinner before a four-course roast on the Sunday.
Darren told OK! Magazine: “We’d go straight into the main course – a traditional roast lamb with seasonal vegetables.”
He added: “They’d also have a compound salad served in a kidney dish attached to the plate – just some lettuce and cucumber with a little mint or some grated carrot and coriander.”
The Royal Family also have their cheese with lunch, rather than dinner, with the Queen being particularly fond of the fresh Windsor Cheese made specially at the Windsor Dairy.
Darren said: “The most incredible sweet white Windsor peaches grew on the estate too in my day. We’d have to lock them away in the kitchens because everyone wanted to taste them.”
