Bottom line is it doesn't matter who the coaches play because it's out of your control. It's really none of your business. Playing time is something that needs to be addressed between the player and the coach .
Your son has a decision to make . If he wants to get tuned up and ready to return to his school and compete for a spot in the fall, which is only 8-10 weeks from now , he may want to inquire about a summer ball league close to home . Some place where he'll get playing time . It doesn't matter how tough the league is. He needs Reps . IMO a kid is better off playing in a men's Sunday league and a low level summer program and or training with a hitting coach, A strength and conditioning coach or even track coach at a local University than he is sitting in a summer league.
Summer time for College players is about adding, getting better. Period. There are a multitude of ways to accomplish that . Summer ball is just one of them . The main thing is that he returns to school better and or bigger , stronger , faster than when he left .