How about classic cupcakes with icing that you can decorate with sprinkles..like dinosaur or fairy sprinkles? Passionfruit ones may not go down well with kids, you could use chocolate chips even.
I make a recipe from Taste called Classic Cupcakes..they last really well in an airtight container and I ice them as well. You could make the cupcakes the day before and ice them the morning of perhaps?
The icing I have used is 1 1/2 cups pure icing sugar, food colouring of your choice, 1 to 1/12 tablespoons of water.