I take dd for a shopping trip to town after school one afternoon. We go to visit the Live Crib outside the Lord Mayor's house. And she gets the presents from her (any that she still hasn't bought) for DH, DGPs etc. We also stop for tea and cake (juice and a bum when younger) and enjoy the lit up street and people watching as it gets dark and magical before getting the bus/train home.
We have a fabric advent calendar that I put foil wrapped chops in daily. When she was younger, I often also added a seasonal colouring page, quiz page or home Ed pages (writing practise, maths sheets etc - but seasonal ones so it's fun) - all free printables from various websites. Just rolled up in the pocket. Sometimes i made a treasure hunt of clues around the house with the last one being a pocket money type toy (a Lego figure, McDonald's meal toy etc) - maybe 2 of those each Advent.
At the start of December, I also brought out the collection of Christmas books and dvds. We gathered them over the years, a mix of picture books, small story reading books and longer anthology collections - some were new, some were 2nd hand from family/charity shops, some were presents from others. The same with dvds - some cartoons, some movies and a mix of how we got them.
The other thing that comes out then is a colllection of Christmassy items that are used over the season but are allowed out before we decorate. A fleece blanket with Santa flying in his sleigh (bought the panel to sew on a visit to a quilting shop in Canada), DD's duvet cover set and red sheet, her snowman hot water bottle cover. The plastic plate, bowl, mug and glass that was her second set as a toddler (her main set was neutral but it was useful having a spare back then and it's still going strong for Christmas now). And a handful of proper Christmas mugs for us all to use. These all go back into storage when we take down the tree every year.
When small, I used to give dd a shoebox filled with strips of different coloured paper already cut, tape and a child-friendly scissors. This meant she could spend 5 minutes or an hour when she pleased on making paper chains, which went back into the box so weren't crushed or thrown out by mistake, and then decorated the hall (and her room if enough) when we did the decorating. But she could do it alone which was great to divert her when we got in from school/work and I needed to get dinner sorted etc.
She always helped make a treat of some sort for school - spiced Christmas cookies in tiny shapes (a playdo set of cutters which we kept for cookies) for years in Creche for the show and party for parents, various cookies of increasing difficulty for her class in school (candy cane cookies are beautiful but so much work!!!), or things like bags of snowman soup or reindeer poop to hand out (they were allowed give a treat to the class for their birthday and DD's was over Xmas holidays).
On Christmas Eve, we still do an Irish tradition that the youngest in the house lights a Christmas candle, and we have a family prayer and reflection around it. This is after a "platter" dinner of lots of lovely nibbly bits to pick from the table (cooked and cured meats, seafood, salad, cheese, beautiful bread etc) - there's always plenty that dd would eat but a chance for treats for us too that she might not like, but she could taste if she wanted. After the candle, we get out the box (that normally holds the Christmas books/dvd collection) where her stocking, plate and glass, new PJs for everyone, bath bomb each for DD and I, posh hot choc for us all etc, are all sitting. And the family copy of "'Twas the night before Christmas" for her bedtime story. Once this is opened up, she sets out her stocking and Santa's snack, goes up for her special bath and new pjs, back down to drink her hot cho and snuggled into bed with the story.
Santa's snack is a glass of milk and cookies we've baked that afternoon. Some years we have time and energy to do these properly while otherwise peeling veg and prepping for the big day. But every year, we make a batch of those same cookies earlier in December and I freeze half the dough - so if we are more frazzled, we can just slice and bake that instead.