Most years, DD came into work with me for a couple of hours (I had to turn up but everyone brings their DCs) and we would meet DH on the main shopping street nearby afterwards for last minute shopping and a sandwich in a coffee shop lunch before heading home.
Once we get home, we all work together on prepping for the following day (peeling veg, making stuffing etc) and baking cookies for Santa's snack. Even very small DC can help getting veg from cupboards, pulling out pots, stirring things together....all with Christmas music playing and we dance around the kitchen as we feel like it.
As for baking, I am not totally cracked - we do the same recipe every year, that we do not infrequently anyway and can be frozen - so I freeze a half a batch from earlier in Nov/Dec so that if we don't have the time or energy to bake from scratch on 24th, I can just slice and bake the frozen dough.
The past few years, I haven't needed to go in every year (I take a full day's leave instead) so we have done a Christmas Eve charity swim locally (very short, DH holds the towels) and had hot whiskies afterwards with the other swimmers at the local sailing club. Before going home for nice sandwiches and coffee lunch.
Then doing the prep stuff in the afternoon.
"Dinner" is "Platter" - take out lots of yummy cold things from the fridge and put them in the middle of the table for people to help themselves. Cooked and cured meats, smoked salmon, prawns, hummus, breadsticks, cheese, crackers, cherry tomatoes, carrot and pepper sticks, lettuce etc.
Once we tidy up from that, we go into the sitting room where the tree lights and side lights are on (so nice low level lighting) and we have a few minutes quiet family time remembering the good and bad of the year just finishing, and those no longer with us. Then the youngest lights the Christmas Candle (an Irish tradition showing that there is "room in our Inn for any weary travellers).
We pull out the Christmas Eve hamper, with new pjs for everyone, lush festive bath bombs, DD's plastic plate and glass with Santa on them (from toddler years) and her snowman hot water bottle, her stocking and the family copy of "Twas the Night before Christmas".
DD puts out her snack for Santa (milk and freshly baked cookies), and goes for her festive bath and into fresh new PJs. Downstairs for a hot chocolate together, and then I read her the book in bed as a nice relaxed bedtime with a fair chance of getting to sleep as normal.