Guitar?

I am thinking to send Little-D for some music classes or maybe enrichment classes like arithmetic to help him with his hyperactive brain.At least he have something to think of when his brain keep on working. Or should I send him to both classes? What music instrument should I start first? Piona? Guitar? or Violin? He seem to have some interest in guitar as when we were at those shopping mall and he saw the best guitar that was at the counter there, he was so excited but I am scared that it is only the matter of time that he will just forget about it as is concentration time is very very limited as what his teacher said "maximum 5 minutes" Really cannot decide..