It would be really nice if people could post their ideas here (largely so that I can filch them) - anything which is reasonably quick/manageable and fairly cheap, which is fun to do, involves tasks small children can manage with supervision, and preferably produces an end result most children will be happy to try.
Obvious ones, to start: chocolate crispy cakes, tiffin, home-made pizzas, pizza omelette/frittata, French toast, little cakes, brownies, spring rolls, little filo parcels with stuff in.......