Fairy lights and greenery, you can’t go wrong.
I have the old 70-80s style coloured lights, but I appreciate they’re not everyone’s cup of tea. I do love the warm lights. Definitely not the ice white or blue lights though. The ice white ones are too harsh and nothing says Christmas quite like the emergency services. I have a sideboard that a garland goes on, plus a garland to go down the stairs and I tuck lights into both of those (not flashing though, has to be still).
If you have any glass vases that you’re not using, or clear glass bottles, you can put them in there as well. I always use battery operated ones if I do that because I worry about them all being bundled up and causing a fire (I know that’s probably insane but it comes from years with a mum who was convinced we’d all be burnt to death in a fairy lights based inferno if we left the room while they were plugged in - I’m not that bad but a bit of it clearly sunk in).
I’d go with lots of greenery. There are loads of florists who are advertising wreath making courses now (they book up incredibly quickly so don’t leave it if you fancy it) and some give you the option of making a table centrepiece as well. And real candles on the table would be beautiful.
I know someone is going to whinge about this but I genuinely don’t care unless you want to compare carbon footprints. When we go to the in laws for dinner, I always do the table. I go for white, silver & greens (think eucalyptus) or navy and gold. Charger plates are a cheap way of making it look co-ordinated and are cheapest in Dunelm. Something that always goes down really well are little gift bags. You can buy them on Amazon quite cheaply. Just clear plastic with white snowflakes on them. I put in some gold coins, a £1 scratch card, you can get coasters with celebrity’s mouths on them, that hook on your nose and are quite fun for photos, so one of those goes in, and one of those puzzles that come in a clear plastic cube with tiny balls inside. Tie them up with a bit of ribbon in your colour scheme and use a brown tag to write their names on, and they act as place settings. It keeps everyone occupied while you’re in and out of the kitchen with plates and bowls. I also sometimes put a disposable camera on the table, although they’re becoming increasingly difficult to find.
For after dinner, I would suggest getting hold of a second hand Wii unless you can borrow one. They tend to be one of those things that just end up in a cupboard during the year, but they’re great for getting great uncle Arthur up and having a dance off with your youngest DS. Or Pictionary is another good one. Don’t ask if anyone wants to play. Divide them into two teams and tell them they’re playing. Put someone on photo duty as well (obviously avoiding anyone you know hates having their photo taken). I think you often get the best photos when people aren’t posing.