I see that your son is a 2018. I think the most helpful thought for you and him is that it is generally much tougher to make it at any level of college than most think. It's not something he'll be able to do "just for fun" as he makes his way through his college years. It takes commitment and a decent level of ability.
I hear some say that there is a school for every player and a decent HS player can find a school to play at but I don't see that play out in this part of the country. I've seen countless all-league players cut from JC, D3 and NAIA programs. I do believe that D3 has the widest range of quality of play and players. But the bottom tier programs take a pounding while playing bad baseball. If that describes the type of program/s your son is targeting, he'll have to ask himself if that's what he really wants.
For reference, one of our former players is at one of the better D3's here in California. As a junior transfer, he sits 87-88, touches 90 and has a decent slider. He is successful but caught in an ongoing competition to stay in the rotation.
Got it. At this stage, we are in info-gathering mode, so we can make informed decisions.
I went to a seminar on college athletic recruiting, and the speaker said to focus on a college that kids can live with even without baseball. He said the average playing career for a college athlete is something like 1.5 seasons. So if you go to a school just for baseball, and you got cut from the team the second season, you'll be completely lost.