Since your going to C&I in Cruz Bay you might want to grab a mooring outside the harbor by Canneel Bay ( a bit rocky during the ferry hours)and dinghy into Cruz.
Cruz bay is small and has a very good selection of restaurants.
You could spend the day on one of the beaches in front of your mooring and dinghy in for dinner.
The next day you could sail to one of the beaches on the North shore.
If the winds are out of the North or NW then go to Leinster Bay on the NE side or go to one of the bays on the south shore.
If time permits rent a jeep for a day and tour the island.