RJM makes a great point about knowing his skillset now and what he will be as a Freshman. It is more important to be ready to play as a regular as a Freshman in a JuCo than it is in a four-year program like a D3. The window of opportunity in JuCo is very short, and like it is now as a HS player, your son needs to be seen playing in games before a college coach is going to want him. There is this perception that kids will go to JuCo and get bigger and stronger and better and then get recruited to a D1, but that is a wrong expectation for most kids.
Yes it is important to find a JuCo that has a reputation as a feeder of talent to D1, but then lots of kids on those teams ride the pine just like they do at the 4 year programs. After their two years are over, so is their baseball career for college if they sit the bench. If a kid does not get on the mound or in the field as a Freshman, they may never get an option to play after the JuCo. Here in SoCal, the JuCo teams are loaded with top talent that would be in D1 schools were it not for inadequate grades/test scores (and these are not poor classroom performers for the most part--the UC schools and even many of the Cal State schools are getting harder and harder to get into, so JuCo becomes the alternative). It is really hard to break into those rosters and get playing time. Those schools already have D1-level talent--they are not giving playing opportunities to kids who hope to become D1 players. Keep that in mind when scouting JuCo options for your son.