Toddler: Bang on pots and pans with spoons. Shake smaller plastic bowls inside larger plastic bowls. Watch as your toddler puts one bowl in and dumps it out repeatedly.
Preschooler: Use plastic bowls with plastic spoons, metal pans with metal utensils, and wooden spoons on a wooden surface (cutting board, small stool). Talk to your preschooler about the different sounds and different materials. See if they can notice anything about the sounds, or if they prefer one material over the others.