Don’t panic OP, this is doable. Try and keep in mind the mantra, “it’s just a big roast”.
Christmas Eve: spag bol if you want to do a big lunch. You can can prep the sauce ahead of time so all you’re doing is heating it and putting some pasta on. Kids will probably eat pasta and cheese, if not the bolognese sauce. Veggie bolognese is easy (bulk out with lentils), and do a separate portion of gluten free pasta.
Teatime: mince pies, sausage rolls, cheese, biscuits. Can put out leftovers on Christmas Day evening, too.
Christmas lunch: pre prep and/or rope in visitors on a couple of discrete tasks (i.e. you can companionably peel potatoes with a glass of wine on Christmas Eve when the kids are in bed). I do a lot of my veg prep including par boiling potatoes on Christmas Eve. And don’t try and do EVERYTHING. However many side dishes you think you need, you can probably delete one. As a PP said, turkey crown is less stressful to cook.
One place to splash on shop bought is on the Christmas pudding and a Yule log for the kids (or ask a visitor to bring) as they are really time consuming and use expensive ingredients to make from scratch.
Make sure you’re got crisps, sweets and tangerines out in bowls so you don’t feel too time pressured. People can snack if cooking is running a bit late.
Breakfasts: get a load of frozen pastries. Bagels. If budget stretches then smoked salmon is nice, or perhaps someone can bring that.
You won’t miss the magic. As long as you avoid slaving away on your own getting stressed, a bit of time in the kitchen stuff Christmas music on can kind of be part of the magic.