So, there are a couple things your son is going to need to do to get an Ivy coach's attention. He's going to have to nail his SAT/ACTs and then demonstrate he's got the stuff to compete at the mid to low D1 level. To accomplish these things he is going to need to take care of business and focus over the next 15 months. For a HA D3 he would have more time probably 18 months. But the bottom line is this is not easy stuff, he has to have something tangible to show any college coach. For your son that may be academics opening the door for athletics. My son and I tried leading with athletics (he was topping out in low 90s as 6'1" 175lbs) with excellent academics. It was a lukewarm response. Once he started leading with academics at the HA schools, he got many doors to open up. There are many ways to get there, and you've got to help your son find his path. I'd get started ASAP mapping out some plans, events and timelines.
So, based on that rising junior timeline, he'll need to take care of the SAT/ACTs first (in the Fall) and keep working on the velo and developing to achieve this goal. Honestly, there isn't a lot of time and you're probably going to have help him get started as junior year is a killer with activities, time management and juggling priorities.
Good luck!