I am biased of course but you should call Kirsten. It is so much easier from St Thomas. Ten days is perfect, sleep aboard first night provision, eat drink and be merry in Frenchtown. Brief at 8:30 the next morning. Dinner in St John. Then six or seven days to bounce around the BVI and an easy downwind one or two day ride through St John's national park on the way back and a ten minute cab ride to the airport from your boat.
Jay