School Band and Orchestra magazine, which goes out to teachers, published an open letter to parents last year about the value of musical instruction. The letter, which you can see at http://www.sbomagazine.com/8190/featured/sbo-guest-editorial-an-open-letter-to-parents/#comment-3321, makes several good arguments about music's importance in a child's life. Better test scores, leadership training, learning to work cooperatively -- and having fun! -- are some of the benefits. I know we've seen this in our family for Greg, and hope that Andy reaps some of these benefits as he starts his first musical activity.
Every time Greg tells me he's decided to take up another instrument -- and another, and another -- I roll my eyes (tenor sax, guitar, bass, clarinet, bass clarinet, flute, harmonica, keyboard, and the latest is drums). But I know that it keeps him fresh and interested, gives him a better understanding of music theory, opens up doors to new performance opportunities (he hasn't had any formal piano training, but plays well enough to be asked to play piano for an improv company; he played sax, guitar and clarinet in a musical's pit band over the summer); and widens his repertoire.
Read the letter! You may learn something about the value of musical instruction that you didn't already know. And maybe it will help you to support your child when they want to add "one more thing."