I have a 6 and a nine year old. Their stockings will have a couple of things from each of these categories:
Food: clementine, chocolate orange, chocolate reindeer, chocolate Father Christmas, babybel, mini cheddars, carton of juice.
Practical stuff: fancy toothbrush, bath bomb, maybe toothpaste, hat/socks/pants/gloves as needed. Hair bands.
Stationery: felt tips/crayons/colouring pencils, writing pencil, notebook.
Stuff we reuse from previous years because it's tradition:
Kazoo, Swanee whistle, finger puppets, fortune telling fish.
A couple of small/cheap toys ( those eggs you can excavate to find crystals/bones, stick on earrings or tattoos, a pack of cards, marbles, dice).
A magazine or comic.