Strumpers, start with a list of the meals you have to do, and numbers for each.
So for Christmas Eve breakfast, you might only have the "core" group of immediate family and ILs - and that might be nice to have in a coffee shop in town enjoying the Christmas spirit (without too much shopping to get last minute - just picking up nice things if you fancy them).
But Christmas Eve dinner might have a few extras (friends, other local wider family members etc) so a buffet meal might work best.
Will you be doing a full-on traditional turkey and ham feast for Christmas dinner? Or a different meat? And do you usually do roast dinners or are you better ordering in the majority of it?
Are there particular nibbles or meals that are particularly loved, by your family or ILs? So a box of Scotch Clan to keep FIL happily chomping, or a couple of bags of Monster Munch for the DCs to do alongside the naice crisps that grownups might eat.
You mightn't be able to freeze LOADs, but you can freeze a fair bit ahead. HM (or M&S or local speciality butcher) sausage rolls work well, and so do HM mince pies. Both can be pulled out and cooked from frozen with just a few minutes extra cooking time - so very handy if you are unsure about numbers, or to do a few times over the few days for different things.
For Christmas Eve, we often do a smorgasbord type meal - lots of things like parma ham, chorizo, salamis, braseola, smoked salmon, cooked prawns, cooked squid rings, sun dried tomatoes, hummus, guacamole, breadsticks and naice fresh bread, sliced up peppers, olives, potato salad (for DD), nice salad leaves. It's not exactly a Swedish version - more a "all our favourite world foods" type thing.
For breakfasts, have normal things the ILs like (toast, porridge, OJ etc?), but also nice treats. So maybe buy a bottle of freshly squeezed juice each day - or squeeze yourself (but who wants that hassle for multiple folks multiple days?!). Nice fresh bread not just the ordinary sliced pan. Real butter. Buy the ready roll croissants/pain au chocolat to bake yourself, or the part-baked packs to just reheat. We get a variety pack of cereal for DD for Christmas week as a treat too. Maybe a bowl of fresh fruit chopped up and some yoghurt, for people to serve themselves.
Christmas dinner - prep a lot the day before if you are doing it yourself. Peel potatoes and soak in water in a pot (to par boil before roasting). Peel and chop carrots, cover in water in an air tight container. Peel and slice onion and put in airtight container (no water). Wash and prep sprouts. Make your breadcrumbs (well in advance and frozen if you can) and the stuffing - can freeze stuffing in advance also. Cook the neck/giblets for stock for gravy (can add the carrot and onion peelings too, and some herbs), strain. There's probably loads more.
Have nice bread in the freezer to take out on Christmas morning for sandwiches on Christmas evening/Boxing Day. That and some sausage rolls etc, mince pies, and lots of tea/coffee/other beverages, should be plenty. If there are favourite tea and coffee brands, or particular drinks (e.g. Horlicks?), make sure you have those stocked up.
Will be back.