In our case, when we had a quiet Christmas at home (rather than trying to eat 2 turkey dinners to keep 2 DMs happy as both were being territorial about their "precious first-borns" and neither could accept that the other was due to host us that year, they'd be host the next....ugh!), we didn't do it as well as we would like (and now have a hormonal teen) but I am also dreaming of how it will improve when she abandons us skips off with glee to live her own life.
Christmas Eve I have generally had to go to work for a couple of hours in the morning if it's a weekday. (Or else you must take a full day's leave). So DH and I would drive in together and have no issues getting parking in the city centre due to the early start. He would wander off for a nice coffee (and realistically, often bought my present then! 
)and I would go do what I needed (turn on computer, enjoy a coffee/mince pie and chat with people, clear any last minute bits and pieces) and be seen, before leaving by mid-morning. (Nowadays, I sometimes use a day's leave and do the Christmas Eve swim for charity in the local sailing club before a hot port and a chat with friends; getting lunch locally and any last minute shopping).
DH and I would meet up and get any last minute shopping we needed, and enjoy a nice lunch together in the city. If we have time and the weather is ok, we like to try and get a walk as well, in the big park in the city or a nice walk slightly out of the normal route home to the suburbs.
In the afternoon, we turn on music in the kitchen and work together to peel veg, make stuffing, etc - the bits we can do ahead of time. (Some years I have brined the turkey, DH doesn't think it's worth the hassle). This also includes the traditional phonecall to DMIL as DH can never remember how to cook the sausage meat for the stuffing...
Dinner is a selection of nibbles laid out on the table that are things we enjoy, many are treats and luxuries, that we can pick at for about an hour. Usually with some nice bubbles. And I will light candles.
(Not everything on this list every year, but a nice mix of cooked and cured meats - ham, salami, braseola, good corned beef; seafood - prawns, squid rings, smoked salmon; salad - cherry tomatoes, carrot sticks, pepper sticks, sliced avocado, olives, mixed leaves; breadsticks and nice crackers, dips - hummus, tapenade, sometimes a few hot things like sausage rolls etc. We usually also open the Christmas cheeses at this meal to make it worthwhile getting a nice selection.)
25th starts with a nice breakfast. Often freshly squeezed OJ or good bottled juice. A large plunger pot of fresh coffee. Pastries from the oven. Diced fresh fruit (that I would have chopped the afternoon before when prepping anyway).
Relaxed showers and getting nicely dressed in time to go to mass. And have a few extended family calls to make (although that's petering out now). But we also make sure to have decent walking shoes in the car also - as we either walk the local pier (a 3km walk) or up and down the 2 hills in the local park (over 2.5km and steep!) while we are out. (We never do any of the local Christmas Day swims as they are all too hectic).
When we get home in mid afternoon (between 2 and 4 usually), we throw the turkey in the oven if we haven't already put it in on the timer. Light the fire, throw some M&S party food in the oven, open wine, turn on lamps and light candles, sort anything in the kitchen that needs to be taken out/turned on etc, and then go to relax in the sitting room.
The nibbles are our starter, to tide us over to turkey. And give us the energy to open our presents. After which, we have a round of calls to family to thank them and catch up. And occasional forays into the kitchen to refill glasses and turn on a pot or move something into the oven or baste the turkey etc - it really is all very relaxed.
We'll have the tv or radio on at some point, and I always have a book I want to read. (If we didn't have the calls to make, I would have more reading time in the afternoon).
Proper turkey dinner, because we enjoy it. But the party food is our starter, so we only sit formally for the main course and pudding. Cheese is usually loaded onto plates to have on the couch later on (maybe while watching a movie).
Stephen's Day is a slower start, but definitely involves a walk by the seashore. Before DD was around, it was leftover turkey sandwiches, beer, later on cheese and port, and lots of reading by the fire for the afternoon.
Whereas now, it is cleaning the house for hosting family and neighbours as it is DD's birthday and we enjoy having people dropping in and out (officially 3pm to 6pm or so - but often the last neighbours leave around 2am, we're a sociable street).
For us, it is a rare few slower, quieter days as work is always hectic, (and with DD, other life is hectic too), and we need to travel for NY at least (always) and usually means leaving our house on 27th if we have suited ourselves and stayed home for Christmas itself - Irish Mammies are great at feeling hard done by.....