we do stockings first thing (8ish I guess) then main presents wait until until after brunch (11/12ish?). I always put in things that will keep them busy for a few hours while the adults catch their breath.
dd1 (16) - make up stuff, a book, jewellery, t-shirt, wallet, water bottle, a mug, bath set, fluffy socks & chocolate
ds1 (10) - nerf gun & various accessories, mug, couple of marvel figure things he likes, t-shirt, couple of little lego sets, joke kit (whoopee cushion etc), pringles, chocolate & fluffy socks
dd2 (7) - a plushie, a hoodie, craft kit, various small playmobil sets, headphones, stationery, mug, chocolate & socks
ds2 (5) - mug, some My Little Pony ponies, animal hot water bottle, trackmaster train things ( track/engine/cars), Thomas mini trains, t-shirt, chocolate & socks.
I tend to put the smaller/cheaper stuff in from their Christmas lists & just a few extra silly things - it really adds up financially when x4!