Welcome 17U Minnesota! Great state!! My 2016 had a couple offers from D3's there and really liked both schools.
If your son will be a rising Senior this Summer, and does not have firm college offers yet, I'll propose an alternate strategy for this Summer 2017.
IMHO, the vast majority of rising Seniors who desire to play in college and who aren't pro or top D1 prospects should focus their rising Senior Summer on college recruiting, not playing a lot of games / tournaments and definitely not playing in a collegiate Summer league.
Much work should be completed prior to this last Summer 2017, e.g., developing a vetted list of schools, contacts established with college coaches and admissions reps, video, recruiting profile, ACT/SAT scores, etc. Then this last Summer is focused on being seen live by the coaches on the player's vetted list of schools, typically at camps and showcases, but it could be tournaments too. It's also focused on visiting schools, meeting admissions reps and coaches on their campuses, i.e., demonstrating interest in the player's vetted list of schools.
Your son's objective is to have a place to play in college that fits his academic and athletic interests. And as a player with D2-D3 skills, as the vast majority of players have, the time to secure that is this last Summer before Senior HS year.