Christmas Day last year my DS was 8 days old. I'd been hit by the baby blues and DH and I were knackered.
We had the day at PIL so there was no running around after anyone thankfully.
However, it was quite a tricky day as everyone wanted to hold DS who got very fed up with being passed around, we had a hellish night that night!
Also the great grandparents just couldn't make adjustments for us, they are so set in their ways insisting on eating at a set time and ploughing through the whole enormous dinner without taking a break. DS just cried and screamed wanting to be fed and held, so DH and I had to tag team dinner. At one point we had to take him out, and they all just carried on the meal (and finished it) without us! It was not how I imagined our first Christmas to be 
So I would make it very clear to everyone that the day might get a bit overwhelming for you and for them to allow for you to take so time out. Also to ask them to go with the flow and that some traditions might have to go out the window.
We were also given the obligatory silly elf outfits for DS, but as a gift on the day, so he didn't get to wear them! Presents like that need to be given in advance so they can be used on the day!
I hope you have a lovely Christmas though, eat lots of
and enjoy how your DC will be fascinated by the twinkly tree lights!