K.K.
T.,
Hi there. Like one of the other Moms said go to the Dollar tree or some please that have foam balls then get the paint and make the plants but to make it move do you have the modile that you used with your sons baby bed. If so you can take that and make it move. Use that and some old wire coat hangers and some fishing line. But most of all you need to let your son help you in what ever way that you decide to make it. I hope that will help you in some ways.
K. K.