DD opens her stocking (and any presents beside it) in the morning, and we enjoy a nice leisurely breakfast (a rarity in our house) - freshly squeezed juice, freshly ground coffee, pastries (baked from M&S frozen or Jus-Rol tubes), fresh fruit (I chop on 24th), etc.
We go to mass in the late morning. We also have at least 1 family call to do after that if we are at home. And we also usually go for a walk either on the pier or through the woods as well.
When we get home (between 2 and 4 usually), we turn on the oven and cook some nibbles while doing other work, getting turkey ready to go in, lighting fire, turning on lamps/lighting candles, opening drinks for everyone etc. So we only open presents once those are done, with the drinks and nibbles to enjoy. After that, we need to ring extended family and pop in and out basting turkey/turning on potatoes and veg etc.
After dinner, it does get quiet, but we usually turn on tv for whatever movie is on then, enjoy cheese and crackers later, and pudding if we feel like it, and then retire, replete, to bed. (I keep meaning to get a game we would enjoy, but DH is not great at games and DD is in a very "anti-other humans" phase for the past few years...so I don't push it).
As every other day is very hectic, that quieter day is much needed to recharge and enjoy in peace.
If we are not at home, we are visiting extended family so spend the entire day running between mass, DMILs and DPs - desperately trying to get a walk in somewhere to reduce the impact of 2 turkey dinners, and a few minutes peace from the chaos of both houses. So downtime isn't ever a problem those years..... :(