Today, we just started considering a week on STJ early summer, fairly last minute as usual! Couple things to think about..I believe most villas might have a 5 night minimum? If you can find a place you will need to reserve a car/jeep rental? unless you rely on the taxi's? Vehicles book up fast, the 2 week window we are considering I found one car rental is already booked up and need to call others now. If I were to try a 4 day trip with 2 families with kids I would probably stay at Gallows Point (walking to restaurants/shops) or the Westin for the beach and other amenities. Not sure I would try it, staying on St Thomas sounds more stress free and you could always pick a sunny day to ferry over to STJ, taxi to Trunk Bay for beach time with good amenities, taxi back to Cruz Bay and check out the shops before heading back to STT. Good luck planning!