I've mentioned this on another post, but exit velo needs to be off a tee. A moving ball will have a higher exit velocity than off a tee. The second overall pick last year (and probably the second best HS bat I've ever seen live) topped at 100 mph. It's unlikely your grandson is at that level.
Even then, exit velo isn't the important number. The important number is pitching velocity and how well he hits good pitching. Anybody can smack around 67 in the cage. How does he handle 85+ and how often is he seeing it. This is why the summer circuit is important, you need to be able to show you can hit quality pitching regularly.
What's his summer schedule like? I'm not familiar with his travel org. Are they hitting the right tournaments or staying local and going to random showcase events? If he is as good as you think he is why has his program not been able to get him in contact with more than two D1 schools so far? Might be best to find a new travel team for the fall. I just watched a "highlight" clip of him taking 5 swings. He whiffed on one and fouled another into the net. Sure it happens, but that isn't something his club should be promoting on the internet.