As a relatively new resident coming from the Bay Area, I find pretty much all of St Thomas safe. However, since you asked, the only thing I would suggest is avoiding walking in the downtown area behind the waterfront. Not many lights and a little deserted. You'll see what I mean when you get here.
As far as your son, heeding the above advice will also help keep him away from temptation. Some people have noted different experiences, but I have NEVER been approached on beaches, in town, etc. to purchase drugs. In contrast to other island paradises where I have been approached to buy drugs at every turn, the popular beaches, i.e. Magen's, Sapphire, and Hull, do not suffer from hawkers around every corner. That's not to say that drugs aren't here, just that your son would have to work hard to find it. If he's going to be in your physical presence for most, if not all, of your trip, you should be fine.
Have fun!

Thanks, I just worry sometimes because my son looks like the kind of person that uses drugs. So he might be a good target for someone to approach.

Well, if your son is working his program, you shouldn't have to worry. You should be asking where the meetings are so he can be among others.
Ronnie

Hello Liz,

If you stick to the resort beaches on St. Thomas that would be good. Some of the non-resort beaches, well primarily Coki Beach, there are some folks who have marajuana for sale and might approach those that look like they might be looking or fit whatever picture the sellers have in their mind of typical buyers. If your son is going out at night by himself or even supervised to bars he can find marajuana if he is persistant and ask around.

All the best with your vacation and I hope it all works out well and he sticks to his program of being clean.

--Islander