In my experince the kids don't usually each much as they're busy having fun.
I would kinda concentrate on the adults but obviously do some kids stuff.
Pizza - kids and adults will eat
sandwiches - do adults and simple cheese spread types fir the kids
quiche
sausages or sausage rolls
bread sticks, strips of veg and humous
fairy cakes- I made my own but they looked like shite, but you can buy them ready made. Must admit mine tasted nice, was just difficult getting people to try them.
Little bowls of sweets like dolly mixtures and jelly babies.
You go really upmarket and sophisticated but it's hard work and expensive.
I'd also use all throw away stuff so you can just stick it all in a bin bag at the end.
There are some great party bag ideas online.