Do you know how long the HS summer season is? Ours is only about five weeks, depending on playoffs. Still time to pursue travel afterward, particularly for good P's.
What I really like about Gov's second post is that it shows how valuable good communication with coach is. Even if player doesn't like the answer he hears, I have a gut feeling this would be the best avenue. Have player ask to sit with HS coach and explain his situation, that he loves his role on the team and is committed but also is at the key point in time when he needs to be active in his recruiting pursuit and has options to pitch for travel teams and is getting interest from colleges as a P. This, being his key Junior-to-senior season, is very important from that aspect. With any luck, and done properly, he may find the HS coach can be helpful in more ways than he is aware.
I don't know the coach and have no idea what the response will be but I still think this is the right thing to do and will be best in the long run even if the response is not favorable for travel.
There are other avenues to keep the progress moving forward with his pitching skills and there are certainly fall camps and showcase events. Also, with NAIA, D3 and JC, the recruiting process continues thru senior season.