Hi Kim,
Has your son shown an interest in learning to play the piano? If he hasn't had any exposure yet but you'd like to see if he likes it, you could buy him a keyboard and let him play with that.
If you're sure you'd like him to start lessons, the only music store I know of is The Music Nook in Milford. They sell and rent plenty of instruments; I don't know about pianos. Or maybe he can go to practice there daily for a fee if you can't or don't want to have a piano in your home. They can probably recommend a great teacher too.
I'm speculating on these options; I don't know if The Music Nook offers them. But my son leased a violin through them last year and I can say that their staff is very friendly and knowledgable. Even though many of the staff are young (high-school age kids) they are enthusiastic and do know a lot. And the violin instructor is the same woman that teaches in the Milford Public School system, so she's very accomplished. It may well be the same for any piano offerings, if they have them.
Good luck!