I forgot one more from childhood - peeling the potatoes and veggies on Christmas Eve. DM and the cleaner would officially be cleaning but in reality having a drink and chat by the fire, while the rest of the family were out in the big city as DF bought DM's present and got any last minute things (and took the other DCs to the pub en route home). I still do the potatoes and veggies on 24th now, as it is a nice thing to do together (DH and DD are also buzzing around the kitchen helping, DH makes the stuffing, DD makes cookies for Santa and we all work together on the Christmas Eve "Platter" dinner).
Some things that we have been doing for a long time in our family, are:
Fabric advent calendar - pockets get a chocolate piece a day, usually a couple of nets of Santa or Snowmen figures from M&S or Lidl, and occasional ideas for things to do that day on a note, free printable colouring/activity sheets to keep DD busy when she was smaller, or roughly 2/3 small toys/treats across the 24 days, like a Lego minifigure or similar.
Christmas bedding comes out roughly 1st of December (a weekend around that) to get good use out of it. We got a duvet cover and sheet set a few years ago in Dunnes or Penneys.
Also coming out then are the plastic bowl, plate and glass with Santa/Snowman on them for DD (bought when she was turning 2, now a teen), the fleece rug with a Santa picture on it (bought when she was 8 on a major family holiday), and 2 Christmas mugs (I have a collection built up over the years, bought and gifted, of a few bits of Christmas crockery but only take out 2 mugs initially to keep it under control for DH). And the collection of Christmas story books (except TTNBC) and DVDs, for everyone to enjoy.
We do a Christmas Eve hamper after dinner before going to bed - new PJs for everyone, lush festive bath bombs for DD and I, perhaps a nice shower gel for DH if I find something, wooden spoons with chocolate to melt into hot milk for everyone, DD's snowman HWB, her stocking, the plastic plate and glass, and the family edition of TTNBC. So a mix of new things for immediate or practical use, and old things getting reused (some of which are in constant use even in December - but put in the hamper as part of the "Christmas Eve bedtime" routine).
DH and I scout around the locality during December for houses with good light displays. We used to do one evening popping DD into the car to drive around and see them all after dark, but she's a bit old for that now - but she still wants to go see certain ones and makes us do different directions to get home throughout December once it's dark to see what is different this year on various ones.
I tend to do a lot of the practical preparations slowly and unobtrusively in the run up, lots of shopping in lunchbreaks etc. I do a couple of nights tackling the wrapping, as there are a lot we have to buy for (and some need early posting), spread out on the kitchen table when DH is on a night out.
But I will always a half day to take DD into town one afternoon after school for her "shopping trip" - to get a present for DH if we don't already have it, and anyone else she needs to, but more importantly, to see the "Live Crib" outside the Lord Mayor's house and to have a hot chocolate and bun together enjoying the atmosphere, getting the bus or train home after dark to see the hustle and bustle. It's a nice time for the 2 of us to slow down in what can be a very busy month (work, school, regular activities, and then socializing around all of those as well as socializing with family/neighbours/friends - nothing to do with preparations for the celebrations!).
DD and I also now have a tradition of making her birthday cake on morning of 26th - we used to buy it in M&S on Christmas Eve after she came into my office for an hour (I had to show up for a short while before they lock the building at 12./30, or take a full day off as leave), and we'd meet DH after his coffee in town to go to M&S for whatever else we needed before family lunch in town and heading home. Now DH also needs to go to work (for the full day!), and DD prefers to bake herself.