@nategasser It's great that your son is getting certified - diving is such a good bonding experience!
My son and I got certified in Cozumel when he was 13, so we were back-rolling off of boats from our first dive. So, my first thought on reading your post is that it could actually be easier to roll or stride off of a boat rather than walking with full gear on into the surf, sand, rocks, etc. Could depend on the specific shore that you are on. If you re-consider boat dives, Cozumel has some beautiful shallow dives to get your son hooked on diving. Key Largo also has some nice boat dives that are fairly shallow.
That said, for shore diving -- I have recently been planning a trip to St. Croix and it seems that there is a good bit of quality shore diving there. Frederiksted Pier, Davis Bay, Cane Bay, to name a few. There's a dive op that specializes in shore dives (
Sweet Bottom Dive Center), which is only about 5 minutes from a resort (
Carambola Beach Resort). I will say that the lodging is roughly twice the cost of Cozumel (but still cheaper than Key Largo), and the diving looks to be about 50% more (though on the plus side for a new diver, most dive ops in St. Croix include gear rental in their prices for guided dives).
@drrich2 has some great research/reports on St. Croix in the
Lesser Antilles section of Scubaboard if you want to read further, and I've found the St. Croix scuba videos here to be helpful:
https://www.youtube.com/c/TritonsRealm