There are a good range of rubber stamps featuring bumble bees that children like. They can make their own pictures with them and use them in scrapbooking. It is also fun to make applique bumble bees from felt.
Consider making a bumblebee mobile. Each bumblebee could be colored and cut from paper, or assembled with craft pom-poms, googly-eyes and glue. Hang them with string from a coat hanger.