BSV is a great choice!! We rented both 3 bedroom units plus a separate unit for us for our large group in July ("kids" were in their 20's) Everyone just loved hanging out at either the pool or in the water. Was a great place for having meals together, mostly breakfast and some dinners. It is within walking to Karakter and also to Maho (which we have done MANY times) if you are worried about them drinking and driving and also because it sounds like they may not be familiar with the island. I understand that concern. Our kids had to stay in the group but then again they are MUCH younger than yours! I would check in with Dave Herbert with Happy Hour Charters. He can set you up with a sail on the Celine Too. Great day with Neil! Everyone in our group loved it!! Also Dave and his lovely wife arranged a dune buggy tour of the island including a lunch stop. Very fun day and again we all had a great time. Fun way to see the island! You could take them over to Anguilla for a day trip. Totally different experience. There are places to rent jet skis if that is what they want. Trust me there is nothing boring about St Maarten!! We always end up on Anguilla just to take a rest from vacation before we have to head back to reality!!