children and interments  

I think that once they start to show a genuine interest in an instrument it is a good time to let them try. I don't know any brand names off the top of my head, but I know there are several starter instruments available at department stores. If he enjoys the bass get him either a bass or a six string guitar. Maybe his older brother could help him to learn a little about it. He should still be supervised while playing with it. You never know you might have the next musical prodigy on your hands.