Your older child knows about Father Christmas. What about the younger one?
An older child can still enjoy Christmas without being put in charge of a younger child’s belief.
Before school breaks up, ask the older child what they would enjoy doing at Christmas. They might help choose a stocking filler or write a card. They might prefer to leave all Father Christmas arrangements to adults. Respect that preference.
Agree on one response
“Your sister still likes the Father Christmas story. If she asks, tell her to talk to us” is easier to carry than “You must never say anything.” It does not ask the older child to act or deceive. Share the plan with grandparents before a lively Christmas lunch puts anyone on the spot.
Give the older child something that belongs to them: choosing a game for Boxing Day or decorating the table. If a younger sibling discovers the truth, keep the conversation between child and parent. If the truth slips out, answer the younger child’s questions instead of blaming the older one.