It is nice to have a "dream school" but your son needs to identify what he is looking for in a school and baseball program. Then see where he fits and what schools are a fit for him. Look at the churn on college rosters. There are lots of reasons for churn, but look at a P5 roster over the years and see how few players provide any substantial contribution, the number that move on, etc... I am aware of a number of players from my area that were really good HS players who went to P5 schools. In most cases they played little or were didn't make the team. One player is with his third team and has yet to have a meaningful contribution and he was an absolute stud in HS. Most of these players could have went to mid majors and had opportunities to show they could play DI baseball. Figure out what you want then see what options there are both ways. It ultimately takes a coach extending the opportunity to participate. Very few HS players realize how good the players are and the level of competition even at a mid major. Try to be realistic in the decision making process.
Dream schools are a dream, HS players have no real knowledge of what it is to be a college student for an athlete in college. Bottom line is that the school he wants to be at if he doesn't make the team or is not satisfied with his role?