I agree that the one time we went to St Croix we found that it wasn't the greatest place to shop. The water taxi at the pier sells a wrist band that would cover you for the day and may be a consideration if you plan to be back and forth. I believe the beach is located on Great Bay and the boardwalk runs along it. There are many locations to rent loungers, etc and drinks and food are both available all around there. The beach did appear to be clean and the sand look very nice. We did an island tour on our own the first time we went to StMarteen and it
really did give us an opportunity to see lots. My brother in law had spent a week there and knew the island very well. If it were me I would probably opt for an excursion rather than drive.