Aw this is bringing back memories of when my now big kids were smalls.
Choose what you start carefully as things become traditions quickly and then you are stuck with it. 😁
We had a basket of Christmas books that came out every year and lived by the tree or by the fireplace (not too close) and the kids chose stories to read.
December 1st the advent calendars, winter bedding (snow scene with animals so used half the year), craft activity or card making kit and something funny like Christmas shaped pasta.
Christmas Eve, new pyjamas so they looked tidy in the morning instead of the usual scruffiness and maybe a chocolate stirrer. Also a family puzzle so the nobody owned it.
Leaving beer, Mince pie and carrot out for Father Christmas and Rudolf before they went to bed.
We had activity calender with little bits of paper in with something for each day, mostly simple stuff that we might have done anyway, dressed up as
"Get ready for Christmas by tidying up room and putting up fairy lights."
Watch film e.g. muppets Christmas Carol
Make paper chains
Make/write cards
Get tree
Decorate tree
Make snowflakes
Toy tidy up /donate to charity shop
Walk to gather greenery to make wreath, garland, table decoration
Trip to town to choose a small present for perhaps a sibling, other parent, local present collection
Wrap small gift and put under tree
Walk to see Christmas lights
Christingle service
Panto
Ice biscuits
Go to school Christmas fair
Go to see Father Christmas
Decorate Gingerbread house
Bubblebath with candles (battery)
Lay table on Christmas eve, they loved this, drawing place cards and deciding where people would sit