Here is my take on collegiate summer ball, which may be a bit controversial.
1. If your son is a solid pro prospect summer leagues are a must to be seen and cross checked and should play every year he is eligible and really work on getting to the Cape League. A pitcher should be involved with Driveline, Wolforth, 3P or some other elite program.
2. If your son is a borderline pro prospect then he should play his post freshmen year and then see how he does regarding the next couple of years. If he is a borderline pro pitcher I would seriously consider doing a driveline, or Wolforth program during his first summer and skip his first year of collegiate ball. If he gets his velo up to solid pro range. (95) then I would consider doing summer ball his post Soph year to be crosschecked by scouts.
3. All college players regardless of skills should experience a summer of collegiate league ball if they are interested in it. It is a unique experience which only college baseball provides. If your going this route, do it your post freshmen year because of 4 below.
4. College players need to realize that jobs post graduation are heavily influenced by summer internships. Most kids get their first job post college as a result of their summer internships. These usually start in post Soph and Jr years so if he wants to do summer college ball, the freshmen year is the best one to do. You also do not need to play summer ball to play baseball at a high level during the college. If your son is tired from his school year then encourage him to take a summer off.
5. It is possible to do a limited summer schedule and still do internships as there are lower level collegiate leagues that only play on the weekends.
6. Although your college coach will drive the process if a player, with some help from friends, family, contacts etc can locate a local team most college coaches will be OK with this.
For background: My son played in the CA Colegiate League (CCL) on a competitive team post freshmen year. He had a great time but also learned what a long haul 55 additional games were after a year of college baseball. He got on this team via help from his HS coach, who knew the team coach and he arranged it and then communicated with his college coach who was very supportive.
The rest of his summers he worked internships and in one of those summers he played in a lover level league with mostly JC kids, a few 4 year players like him, as well as some high level HS kids. His internships resulted in him getting into a fully funded masters program after he graduated college. Had he not done the internships he would not have had access to this scholarship. Most of his friends got their first jobs out of college due to their summer internships.
My point is that summer college ball is great for those who want to play, but is by all means not necessary and in some cases I would argue that it is better to do summer workouts with Wolforth, Driveline, 3P or another elite level training program, particularly for pitchers. Getting to 95 plus is more important for them than playing summer ball. If you do play summer ball you will be limiting your post graduate job opportunities.