Stan and I took the ferry (sans car) to Nantucket last May and hooked up with one of the many taxi/tour guides that are parked just off the dock. The female driver is a local resident who picks up extra $ during the tourist season driving people around the island. She was super nice and very chatty about the island. She drove us to Sankaty Head Light where we took a number of pictures and had we wanted to walk to Great Point (about 2 miles each way!!), she would have waited.
Coming in by ferry, we got some great pics of Brant Point and Brant Point Range Lights.
There are a number of shops near the dock with food, gifts, etc.
One of the web pages I logged onto a few minutes ago indicated there are "5 major road-separated paths covering 25 miles" for people electing to rent and ride bikes or mopeds so that mode of transportation is available.
Hope your weather is as good as ours was.