You said you have some room in the freezer, I think you should use it.
I despise not enjoying the Xmas day if I am in the kitchen cooking meanwhile everyone else have fun, so I prepare almost all meals for the week in advance. Ideas:
Curry night, meat and veggie version and is gluten free easy. Fully cook and freeze. For the kids prepare in the freezer some plain meat to just be grilled. Served with rice and veggie stick. They can get a bowl with the sauce to dip.
Italian night, cold cuts, cheeses, olives and pickles, bread and gf bread (get the ones that need part baking) kids get pizza, adults veggie lasagna, all from the freezer.
Breakfasts, toasts, cereal, in Xmas day, bake at home pastries, will the kids eat pancakes? The freeze incredibly well and just serve them with nutella and spray cream 😋
Xmas dinner, if they eat roast is great, add a bought veggie main. Yorkshire puddings, potatoes, carrots, parsnips, cabbage, pigs in blankets, stuffing, gravy all freeze great. Just have to cook the meat/veggie main. Get a pouch of veggie gravy, cranberry jar, bread sauce.
Kids get ice cream for pudding and adults mince pies, Xmas pudding.
Highly doubt anyone would want dinner after getting into the selection boxes.
Also make the cooking a family affair. Don't wait for them to offer, but allocate tasks to everyone. Kids can set the table!