Last year my daughters were 11 and 7, gifts that went down well:
Lego - brickheadz or the polybags.
Scratch art sets - they had harry potter and a llama one but loads of variety around.
Fleece blanket and a hot water bottle.
Their own treats - pop tarts, America sweets (could wrap up in a new lunch bag/box)
Build a bear pokemon.
Games - exploding kittens, uno, top trumps, payday, jenga, cluedo, logo game. (I've ordered them dobble, monopoly deal and considering linkee too).
Adult colouring books and a pack of sharpies (or nice pencils if they aren't your own children!).
Snowglobe.
Nice money bank.