Agree with advice above, a crewed catamaran would definitely be the way to go. Other things you might mention about BVI charters:
- sailing is the ONLY real way to see this part of the world
- BVIs are simply one of the worlds most perfect sailing areas, if they don't enjoy it you'll never hassle them for sailing again!
- the snorkelling/diving is absolutely out of this world
- waters are protected - no waves/sea sickness, or at least it can be avoided
- rum punches/good food never more than a swim away
- ..in bath warm waters