I'm not much of a singer, but I was in a children's choir for several years, until about 14 or 15. I learned to read music, to use my voice (projection, intonation), leaned how to breathe so I could hold a note. I grew to appreciate all kinds of music, from religious to pop to classics to seasonal folk songs. Right now, I play taiko (Japanese drums) in a small band.
As strange as it may seem, it helped me a lot when I started swimming lessons, because I had a better understanding of rhythmic (sp?) breathing than the other kids in the class.
I think your son would benifit from any type of music related activity, as long as he enjoys it. I would suggest group rather than individual lessons, for the fun factor.