I divorced when my dc were young so I gave up on the concept of 'everyone-together-magical-day on 25th December'. For me, and us, Christmas has always been on which ever day we celebrated it. One year it was on 1st December (dh and I were going to Australia for a month) - that advent celebration was one of the best and we still have some special advent events.
Presents get opened on whichever day we are celebrating with wichever part of the family.
This year we have very long and protracted celebrations. My dsis (from Australia) is coming mid November so there will be a festive theme to everything we do - think turkey, stuffing, sprouts and cranberries in a burger bun! And Christmas cake.
There's a grandchildren Xmas event in the first week of December with all the best of the Christmas snack food - picky bits on steroids! And Christmas cake.
There's a school carol concert with all the mulled wine and mince pies.
We've organised lunch in a restaurant with SILs and BILs where gifts will be exchanged. And opened.
There will be something else with dc and dgc close to 25th but I don't yet know when and I don't yet know what... But full of games.
On 25th, dh and I have a restaurant chef prepared dinner (one of those things where you finish it at home). Just the 2 of us. We'll have fizz at 11am and start cooking and will go on until about 5pm. No telly.
Pure joy.