Mercedes - would humbly suggest that you tell both sets of ILs that you are having Christmas on your own this year, as it's DS's first, but that you'd like to come and visit afterwards.
We've done this for yonks and they're used to it now. Actually, even better, is to get the visits over with the weekend BEFORE Crimble so the dread of having to prise ourselves out of our house & routine and drive to the other side of the country isn't hanging over us. We use the excuse of wanting DCH to wake in their own beds.
The first year we told MIL we wouldn't be there on the day, I don't think she believed us. DH had told her.(I finally got him to see sense.)I'd just put our turkey on to cook on Christmas Eve when the phone rang - MIL in hysterics. She begged DH him to come 'home' after all, told him that there'd be an empty chair at the dining table for him. Reminded me of Macbeth. Note not begging me to come.
Anyway, our first Christmas as a family was our best ever. Eat, drink whatever you like, watch rubbish telly without snooty person in paper hat in the corner saying 'We NEVER watch Coronation Street'.
While I'm on the theme, DH & I lived together for 13 years before we got married, but ILs didn't accept me until after wedding, in fact until DTWs born - never a birthday card, never asked after me. Typical conversation I overheard:
DH - "Yes, I'm fine, working hard, you know.."
(silent for a bit, then..)
"Yes, she's fine. She had a rose thorn in her paw last week but the vet got it out OK. Yes, see you!"
True.
My tip for a stress-free Christmas day - prepare EVERYTHING on Christmas Eve, and start in the morning. Lay table, get crackers etc, make bread sauce, sausages with bacon, prepare veg, put turkey in oven & set timer. Haven't died of food poisoning yet.. Best of luck!