C.W.
Hello, D.-
It's great to hear that your son is interested in music lessons! I have several ideas for you to think about.
First of all, if this is your son's first experience with music lessons, you may want to lean toward encouraging guitar if that is what he is most interested in. Sometimes when children are asked to playing an instrument that they aren't excited about, it can become a difficult experience for the whole family. Even worse, one early bad experience may lead to discouragement and leave a bad impression of music in general. This is definitely a worst-case scenario, but it is something I've seen happen to some children.
I have recently begun teaching myself to play the guitar, so I am familiar with the tender fingertips that turn to callused skin after playing for a while. He should not develop blisters, however. The type of guitar and strings used will make a difference, and you can consult a more experienced guitarist at a place like Music Makers, Heart of Texas Music, or Strait Music to make the best choice. The key will also be to ease into playing by limiting his practice time at the beginning. When I first started, I kept my practices short --stopping when my fingers began to hurt...about 5 minutes at the beginning! As I continued to practice, my calluses developed and my playing time has increased. I have found that it helps to practice a little each day-not only to improve my skills, but to keep my fingers tough. If too much time passes, they become more tender. If your son is really excited about guitar, he will not be bothered by the sore fingers and calluses--they are something he can show off! - A right of passage to being a guitarist!
Finally, all this said, I think piano is a wonderful beginning instrument. Basic music theory, note systems, etc. are based on the keyboard instrument. The knowledge acquired from playing piano is transferrable and makes learning to play other instruments easier. The piano, however, is slightly less portable than a guitar. :-)
I hope this has been helpful! I didn't intend for my response to be so long!
Best Regards as you begin this adventure!