OP this could be a good opportunity for you to reset your Christmas expectations as it were- have a low key Christmas and I think you will be pleasantly surprised about how nice it is.
Don’t get me wrong - I absolutely love Christmas, there’s me and DH and DS9 and DD6, and we do fairly low key as DS has ASD so we need to keep some balance of routine, not have too much noise/colours etc, so we have a tree and windowsill decs but that’s it, so you could do a tree and then some paper-chains.
We have a lot of lovely food, but even that is pretty much what we eat all year round - so lots of fruit, a fancy roast dinner with all our ‘favourites’, ice cream, a chocolate cheesecake, and then for Boxing Day a buffet that has all of favourite party food - sausage rolls, cheese and pineapple, picked onions, egg butties, crisps etc!
You don’t have to go all out, every meal doesn’t have to be special- just focus on things you like.
And presents - we don’t have mountains of presents here, we do a few little bits each (cuddly toys, barbies etc) and a ‘main present’ (usually Lego or toy kitchen etc) we also ask for books/annuals/colouring/craft from family.
So for grown up children you could do a few nice bits related to hobbies/interests and some fun bits - grown up games like escape room boxes etc.
Well I hope that has given you some ideas. We love Christmas in this house!