We follow (approximately) the Danish custom and have Christmas Dinner on Christmas Eve, at my Mum and Dad's. My brother and his wife are there too and occasionally other close friends of the family.
We used to have turkey, then we tried goose but recently Mum has been rigning the changes - I think this year it is going to be a large roast fillet of beef. We have a nice but simple starter - soup or smoked salmon or something like that.
The piece de resistance is the Danish Christmas pudding - a rice pudding with whipped cream and chopped almonds (and one whole almond) folded through, served with black cherries in syrup. Whoever gets the whole almond (no prodding and poking, nor any hiding allowed), gets the almond prize - so everyone has to keep eating until it is found!
It makes Chritmas Day nice and relaxed for Mum - just cold leftvers, reheated soup - and traditional Christmas pudding (put on to boil!).
We tend to stay over, have Christmans breakfast, open some of the presents, then go home, open the rest of our presents and then have OUR Christmas dinner - until this year, a romantic meal for two (starter, roast pheasant and traditional Christmans pudding - and loads of GOOD wine), but now that ds is 4, I suspect he will want to join in!