Tie heavy string, yarn, or a shoelace around the top of a pine cone, then knot it, leaving enough string to hang the pine cone. Have your grandchild use a popsicle stick to thoroughly cover the pine cone with peanut butter, then roll it in birdseed.
Have your grandchild cut a shape from slightly stale bread with a cookie cutter. Spread peanut butter on the bread shape, then sprinkle on birdseed. Poke a hole close to the edge of the shape with a pencil or straw. Let the bread dry until it's hard, then loop string or yarn through the hole and tie it.
Have your grandchild string round oat cereal or pretzels onto heavy string, yarn, or a shoelace. When he's done, tie the ends together.
Hang the feeder outside near a window where your grandchild can watch the birds eat.