Silliness - we do jingle bells around the house on Christmas Eve, in a conga line, every room. The kids play instruments and the pets accompany, all lights off and we carry candles. No one broke a leg yet..
I think getting a set of bells so your partner can go outside and ring them when Fr Christmas is approaching always adds a bit of magic (and gets them into bed fast)
A play a few days before - it can be panto but there are lots of more creative kids plays, but the rhythm of a regular day, going to the same theatre, going out for pizza / burgers after etc, creates a tradition
Decorating the tree together a few days before, going to cut the holly. Pick some timeless music that you will all like ( Abba in my house)
A good Carol service, with candles in the weeks before
Going to see the Christmas lights turned on in your local town at end of Nov - maybe meeting a mate w kids the same age for tea after
Getting then to help with making mince pies
Some familiar Christmas Eve and Boxing Day traditions - like always a Scandi style smorgasbord on Christmas Eve, followed by a movie, and then leave stuff out for Fr Christmas
Boxing Day, a walk and go to the local pub, and then cold cuts and fresh roasties or whatever you like
Boardgames - triv and monopoly or whatever you like
Bigger experiences
Going to an outdoor ice rink
A local garden that’s lit up - like Kew - but they are all over these days
Indoor ski slope maybe