Let child cut out different foods from newspapers and magazines. Glue pictures on paper plate. Do one for each meal. (breakfast, lunch, snack, dinner) Allow child to decorate a sheet of construction paper, color of choice, as a placemat. Glue paper plate to paper. Then discuss why each food is or is not healthy for you or your teeth, and what food group to which it belongs. Make suggestions on healthy meals.
With preschoolers: play house after activity is done and interact with child as he/she feeds their baby what's on the plate. Talk to them on why we would or would not feed a child certain foods.
This activity can be varied to make more difficult.