Do you want to have a few statement pieces - like the tree with gorgeous lights (you can never have too many lights
) .Like all things there's a trend. Bright white one year, blue one year. Last couple of years have been warm, golden lights.
I bought some of the tiny glow-worm lights (IIRC B&Q) which are pretty.
Decorations, (child friendly) those Christmas Shops that spring up are good. M&S , John Lewis all sell lovely ones.
We have a wreath for the front door , battery operated with a 6 hour timer. Flashes or steady lights.
Costco do the huge USA style outdoor decorations (from Nativity scenes to bauble wreaths, Nutcracker Soldier to Father Christmas)
You could get some nice Christmassy plates (like Spode or Portmerion) TKMaxx had some. Just one or two for tea-time.
When my DS was little we had an interactive singing Santa (pure tat) but he loved it.
I'd get a really lovely stocking, one that will last years and will be a decoration up to Christmas Eve
And flameless candles - atmospheric and safe.
(We had a fibre optic tree when DC were little. It was nice at the time but probably way out of date now)