A great activity to do with preschoolers is to cut veggies in half and use the inside- side as a stamp. Dip the veggie into a thin layer of tempera paint. Great gross motor excersize for the little ones too with lifting the stamp out of the paint.
We used a bell pepper, onion, carrot, corn on the cob, and squash which created a variety of shapes and textures for the kids.
In the everyone had a veggie print tote bag to take with them to the Farmers Market.