My plan - for probably next year (still have a nominal believer at least) is to:
Still put up tree and decorations as a family event (but any who do not want to participate are not forced into it)
Still have youngest light Christmas Candle on Christmas Eve
Still do new PJs before bed on Christmas Eve
Still leave out stocking for DD - but add in stockings for DH and I. DD will be allowed put things into ours, but DH and I will mostly fill the other one's, and we will fill DD's too. For fruit, sweets, a book, some useful bits and pieces, and some funny stuff. As a FAMILY thing not an FC thing.
Still do special baking for Christmas - but again allowing those not wanting to participate to opt out.
Last year, we went to a "Carols by Candlelight" concert in town, in the evening, and had dinner in a restaurant before it. Worked very well and DD felt quite grown up being out that late (she was almost 9). But also enjoying the bustle of evening in town was nice.
I plan on getting a few more grown up board games over the next couple of years, to enjoy together. Things like games nights with big bowls of popcorn or crisps and nice drinks, and being sociable together.
Enjoying more grown up tv and movies together.
Making home a cosy and relaxed place to be, but with no expectations. So they can feel free to curl up with a book, or play on the computer, or have friends over, and not have to be "Little Miss Jolly" in with the grown ups - yes they must be polite and acknowledge visitors are present, and come to greet family etc - but they can slope off to their rooms too at times, and not every hour is scheduled with "fun" but there is time to relax by the fire companionably or alone.