In my experience so far, if you are aiming for schools out of the area, I think the Arizona Fall Classic (did sophomore last year, junior this fall) is right up there. Check their website for colleges attending and see if it lines up with your son's targets.
Stanford camp was extremely productive (though expensive). Obviously dozens of colleges. Again check their list to see if it matches your son's targets.
If you're interested in schools in the Carolinas/Virginia area, my son played at a Dynamic Baseball tournament that was productive. One of his team's games had 15 colleges.
If you get an AC tryout, take it.
Ultimately, I think this kind of question can be best answered after knowing your son's targets. For instance, Headfirst and Stanford might be fantastic for him, but they wouldn't be good for a kid with a 2.5 GPA. Dynamic might be great for a kid interested in that area, but wouldn't make sense for a kid who wants to stay on the West Coast. Etc.