OP, just give the games nights etc a go. With our DC we plan stuff in advance, even if it's all stay at home, but it gives us some dates for the diary.
Film nights. Each person gets to choose a film they think the whole family could watch. Homemade pizzas, popcorn, diet cokes, watch in the dark.
Spa night - buy some face masks, nail polish, hot cloth and hair treatments etc online and have a girlie night, diffuser scented oils. Make sure everyone has clean stack of towels, PJs and bathrobes. Put on silly ambient music, light candles, run deep candlelit baths etc. Do each other's toe and fingernails. Help with lash or brow dyes or shaping or fake tanning. Just do the stuff they enjoy - don't force anything.
Casino night - low lamps, card games, jazz in the background. I'd never suggest playing for money - not even penny stakes, but playing for counters or matchsticks is surprisingly fun. Poker, blackjack or cheat are all good.
Theatre/show night. Record a ballet or live play that's on TV over Christmas and sit down to watch it together. Have a glass of champagne (or mocktail for younger one) beforehand, and choc ices or mini ice cream pots half way through. If they get into the spirit you can dress up. When we did this in first lockdown, one DS was in the DJ he;d bought for the prom that never happened (
) and the other was in PJs.
We're also all writing a few questions towards a bumper family Christmas quiz. Everyone picks a subject they like or know about and writes about 6-10 questions.
Board games or word games like scrabble/bananagrams or those personality games.
Even a night of old fashioned parlour games. In desperation during first lockdown, DTeens suggested a game of Hide and Seek. It was hilarious. Way more fun than we thought it would be. They've asked to do it this Christmas again and they are both old enough to be at uni.
Look up some pretty walks in your area. Take a flask of cocoa or some Christmas treats and take photos as you go.
Cook together. Christmas baking or health conscious New Year stir fries, salads, soups and smoothies.
Make cocktails and mocktails together for an evening.