When we make pizzas as a family, we put what they can eat out on the bench-top and then let them pick and choose from our selection. I call it 'the art of controlled choice,' and I've blogged about it before when the girls were making a pretend-pond on a mat.
If you want to have pizza too, set a good example and rather than just scattering the ingredients on top of your pizza, show them how easy it is to turn a pizza base into a canvas, and craft a face, landscape or treasure map. Be sure to set an even better example and EAT what you make.
Best wishes for Halloween everybody - have fun and don't eat too much candy!
Linda.