MC,
We have son's the same age and I'm thinking we live in the same general part of the country. My son is a LHP/outfielder sitting about 80 right now. He is a few inches shorter than yours and his velocity has shot up over the last 9 months or so (sat high 60s as an incoming Freshman). You've gotten a lot of great advice. After reading this site for a couple years and talking to my son's coaches, we've developed a plan for the summer that sounds similar to yours. I'll PM you with his plans.