My suggestions would be...
Do present buying and card writing early to get it out of the way.
Think about what festive activities you want to do in December, they don't have to be expensive - Christmas movie watching, Carol service, going to see the lights, making Christmas cards/decorations etc.
Christmas Eve box - new PJs for all (not necessarily Christmas themed), Christmas book for bedtime reading, stockings to put out for Santa, sweet treat. Doesn't need to be fancy or expensive. Ours appears just as DC we're getting out of the bath each year to the sound on jingle bells in the distance (musical bell shaker)
On the day, DC bring stockings to our bedroom and they get opened there before we go downstairs.
Coffee for me and DH then about an hour of present opening before breakfast. We have something that can be mostly prepared the day before - baked French toast ready to go in the oven or Nigella muffins with yoghurt and fruit, along with something from a selection box. Buck's Fizz for the grown ups.
The morning is taken up with present opening/playing with/setting up new gadgets, phoning or FaceTiming family to thank them for presents and getting showered and dressed.
If it's just us at home, the Christmas starter (soup usually, made in advance) is had at normal lunchtime. We do the full turkey and trimmings around 4.30/5pm. We prepare as much in advance as possible and have a timeline all prepared. It's fairly relaxed with DH and I taking turns to do different tasks. We might put a Christmas film on during the food prep time, so easy for one of us to duck out for 5 mins to put something in the oven etc. Enjoy Christmas dinner followed by dessert.
There's always a new board game under the tree, which gets played either in the afternoon or after dinner.
Cheese and wine for DH and I once DC are in bed.
Boxing Day at home is always left overs and buffet food. Put out early afternoon and people graze whenever they are hungry.