When I was little, the day started with stockings on my parents' bed - my dad brought them upstairs as we never had them in bedrooms, largely because of my pronouncement that I didn't want a strange man coming into my bedroom! Stockings were generally useful things - shampoo, bubble bath, toothpaste and toothbrush, underwear - with satsumas, some chocolate and a couple of small fun things, like bouncy balls or fortune telling fish.
Then we got dressed and my grandmother arrived for breakfast (always french toast and maple syrup), and then presents under the tree from Father Christmas, my grandmother and overseas relatives. Presents were opened one at a time so we all saw what everyone got. Then my grandmother left to go to one of my aunts' to do their tree presents, and we had lunch (bagels and smoked salmon).
Afternoon was quite quiet, playing with presents, until 4ish, when we went to my aunt's for the big family Christmas meal. There were four families plus my grandmother and assorted others, so lots of presents to exchange with cousins and aunts and uncles, and then turkey and all the trimmings. The food preparation was shared out, so nobody was left slaving all day in the kitchen.
Finally, there were games, generally charades or pictionary.
That meal still continues (not this year, obviously) but has been moved to the weekend before Christmas as we are scattered over the country, and as we have settled down, there are far more in-laws to add into the logistics.
Christmas Day for us know is the four of us. It's complicated by the fact that DH is a vicar so has a midnight service and then two or three on Christmas morning, one of which is at 8.
Assuming someone else is doing the 8, we start with stockings - one of us goes downstairs to see if he's been and brings them up. Santa does the stockings for DS9 and DD4, and DH and I do each others. Then it's breakfast and church, and wait for DH to get home.
After lunch we start on presents, but we take it slowly, with frequent stops when something has been opened which the kids want to play with. Last year it took so long that we had to hurry up and finish on the 28th as we had friends coming to stay!
Christmas dinner happens on Boxing Day unless that's a Sunday, in which case it moves to Monday.
It sounds tricky for small children to wait so long to open their presents, but to them the Christmas they have is just normal. I think bringing in a slower Christmas could be challenging, but if you can start before there are memories of last year, it will probably be pretty smooth (depending on your children's personalities, of course).