Pompeii plus the towns on the Amalfi coast is a lot to try to fit in one day. When we were there we met our driver at 9:15, and just barely made it back for the last tender back to the ship, without Pompeii. I suggest enjoying the towns at leisure, and doing Pompeii another time, unless your ship doesn't leave until later in the evening. A private guide for this is wonderful, as the big busses the ship uses cannot get into Positano town.
