Some great advice here!
Buy 2-3 potato peelers so people can help.
Let people help. It’s a good icebreaker and they relax more if you’re not stressed.
Check your glassware, cutlery, plates and table cloth is all present and correct at the start of December. Borrow more as you need to or get some cheap additions from IKEA ahead of time.
Prep veg on Christmas Eve where possible.
Plenty of croissants/pain au chocolate on Christmas morning so people can grab what they would like and not be too desperately hungry for lunch.
Lay table on Christmas Eve.
Write yourself a schedule so you know exactly what needs to be done, sequentially, when. Put it in your phone if needed. Takes the pressure off.
Make someone in charge of drinks - charging and recharging glasses.
Make someone else in charge of coats/music.
Wear something comfortable but glam - black always good so if you get splattered with something when cooking it is less obvious/easier to hide!
Don’t forget to order in dishwasher salt/tabs/foil/bin bags/napkins/candles ahead of the big day
Cut corners where you can. People will remember if they were made welcome and had fun. They won’t care if you were up at 4am making your own stuffing.
If you think your way through the day in advance and make a list you will feel more in control and, most importantly, ENJOY it!
Set your phone alarm for a couple of moments during the day so you remember to take a beat and appreciate everyone being around you. Like your wedding day, if you don’t make sure you stop to appreciate it, it is suddenly over!
Have board games, charades, conversation starters to hand. If things start to get tense, deploy as helpful to move things to safer ground.
Make sure you have things planned to reward yourself late Christmas Night or on Boxing Day. A hot bath, a movie you love, a walk you especially like to take…
Good luck, it will be brilliant!