Welcome to the site! Part of it depends on what else your son is doing in the summer. My son (current D3 player) went to Headfirst once, in August before senior year, and it was great for him, lots of D3 interest. But, he had played a full summer of travel on a team that went to Georgia etc., and had been watched by various coaches (D1 and D3) before he went to HF. He had also done a state PBR showcase and one D3 individual camp. We had no strategy whatsoever - I only found out about HF on this site, no-one we knew had ever heard of it.
If your son is playing travel this summer, have him email coaches at his top schools of interest now, with video if possible, giving his summer schedule, and asking if they will be able to see him anywhere that he is playing. They will, of course, invite him to their camp, but they may also tell you which tournaments or showcases they like. Also, if you have a travel or HS coach who can recommend your son, have them reach out to colleges. Even if their contacts are primarily local, have them contact some local schools, D3 coaches talk to each other, especially when they spend weeks together at these showcases.
I agree with VA_mom about distance, and about pitching.