Chico:
It's really a tough decision on when to send a player to HF summer- especially if looking at High Academic D1s/Ivies. Son went to HF the summer before junior year, just as your son is positioned to do. He had done some showcases previously and HF (and Showball Magacamps in December) were the events which had the highest # of schools that showed interest in him and he was vetting. He had something to show (top 60-time), and many of these schools had video and transcripts. My son is a position player, who showcased as a MI/CF.
For some schools on his list at the time (e.g. Bucknell), their focus was on the year previous to his--they really weren't looking until September to turn the page and look at his graduation year. Son was looking at the Ivy League, and I think had HF been "the event", August as a rising senior would be too late for D1/Ivy. The D3s at HF even early showed interest, though with their timetables, HF rising senior is right as decisions are starting then, after a number of D1s have filled rosters.
Fenway's point in bold print, was spot on; my son and I saw it first hand. After ranked Big State U. offered my son, the timetable for where he would eventually commit accelerated. Good luck to you and Chico Jr!