Good tip on the tele the other day. Fully cook the veg the day before (carrots and Brussels certainly) and then drain and put in a zip lock back with as much air removed as possible. Then just pop the whole bag (or a couple of bags) in a pan of boiling water to warm through. Or tip out to sauté.
Par cooking potatoes tends to make them go grey, so yes you would have to freeze.
Other things I’ll do - mash, bread sauce, red cabbage - all made and frozen. Stuffing will be made the night before. Turkey will be put on the roasting tray, stuffed with an onion and wrapped in bacon, wrapped tightly in foil and put in the fridge ready to go. I then open the foil, put wine in and reseal tightly and cook via the Phil vickery method which is much quicker, then leaving the oven free for the roast potatoes which are the only thing I’ll do from scratch.
And yes, it is only one meal. But my house layout is odd and the kitchen is on a half floor different to the living room so me cooking while they all sip gin and relax makes me feel like the family servant. So I do as much as I can so I get to chill out too.
I’ve worked out I’ll be serving 182 servings of food over the next 6 days, so as much as I can do before they all descend tomorrow night is pretty much essential.