You already heard from PG so you don't need me to chime in - but as the parent of a RHP (2016) with numbers not near those velo wise and grades slightly below who attended HF on LI last Aug I would say you will get a lot of interest at that event - assuming he kills it day one in his first game pitching.
Make sure he's in contact with the schools he is interested in pre HF and then have him find those coaches onsite once you are there to have him ask them to come watch him pitch (they give u a booklet with their pictures). Good luck and let me know via post or PM if you have any questions about HF. The event was key to my son finding an academic D3 fit and the staff was very helpful and went above and beyond to help me post event.