Dreams are a good. "If you don't have dreams, you have nightmares"..... was a frequently used phrase in my house when my kids were looking at colleges. I think it is great your son is thinking big. I also think underclassmen get caught up in the hype, branding and marketing that goes on in college basketball and football. College and college baseball is a VAST universe of options that need to be explored to know what is possible. Keep pursuing the dream school, but also begin pursuing other alternatives and options. As the saying goes, "you're only as good as your options". This is so true in college baseball recruiting. If a college coach isn't feeling compelled to make an offer because there is no reason to, then he probably won't. As others have pointed out you need to make it known your son is interested, and there needs to be a big reason why the coach wants him committed to his program and taken off the market. Give the coach as many reasons as possible.
Good luck!