My 3 year old loves pealing carrotts and potatoes, and I'll let both of them (3 and 1) loose with a table knife and mushrooms. DS1 also likes grating things. Making their own sandwiches and wraps is a hit.
Bread is also popular - could you introduce more veg into home made loaves?
Baking is good - cakes, biscuits, banana cake (sliced banana underneath a sponge cake)
Both DCs love to 'help' with the cooking. I wanted to make something that they will both enjoy eating - both a little bit fussy and rubbish with eating veg - that they can both have a hand in helping to make. We have done home made pizzas to death...any other ideas ?