Just add a little Velcro to attach the balls so that children or adults with developmental disabilities can simply give it a push. I like using this in a group because each person can take a turn going 2-3 times and then watch someone else take a turn. It worked really well when I asked a lady with hemiplegia to take turns pushing with right and then left. She usually refuses to use the spastic arm, but she didn't seem to mind when I kept moving the bowling alley so that she alternated which arm she used.
I used 2 balls that each made fun sounds when rolled.