I let my kids go to the grocery store and pick the items they want to make their very on Pizza. We get the crust, and the toppings they prefer.
When i get home I preheat the oven , and put each topping on a seperate plate. Then I pick 2 things , each one of my girls can put on the pizza, that way they are not arguing over who gets to put what on the pizza. They just love it. It is great on those days its too hot outside for them.