My kids are all adults now so many of our traditions have mutated over the years, but the ones that have stuck are:
big buffet tea on Christmas Eve (now carried on mostly because people are travelling and turning up at different time), but there MUST be baked Camembert with fresh bread as one element.
Muppets' Christmas Carol on Christmas Eve before bed.
Buffet breakfast on Christmas Day. I put presents under the tree in a different container every year instead of stockings and that container is also a present - so last year it was garden pots, year before was Seasalt bags (they had stockings when younger but moved to 'useful' as they became teenage).
Presents are opened throughout the day rather than in one massive ripping off of paper, again initiated once they were teenagers because they complained that 'Christmas was an anti climax once the presents were open). So we started rationing them out once all the kids passed the over excited tearing off the paper stage.
Long walk before sitting down to eat dinner in the evening. Started this because they never wanted food earlier because of all the sweets, so they needed to be removed from chocolate sources and given an appetite, now continued because we all have dogs.
Christmas evening is games. New games they've been given or old favourites (now Cards Against Humanity!).