We have been to Trunk Bay and thought that it was a beautiful beach. Last year when we were in St. Thomas we decided to go to Magen's Bay. It was a great day and we rented chairs and enjoyed the beach. There were places to get food and drinks. It was a great day without the hassle of taking the Ferry to St. John.
Next summer, we will be in St. Thomas again. We may head over to St. John since our kids have never been. Otherwise, it may be another beach on St. Thomas.