Nantucket

I do have some more info though I would't call it a full trip report, Where the ferry docks there is both motor bike and peddle bikes shops. (we brought ours) Pay for the Whaling museum, they will give you a pass for the windmill tour and other stuff that I can't remember. Down town has cobblestone roads so you will have to walk a couple of blocks before you are back on paved road and able to bike. We biked to surfside beach which does have the bathrooms and changing stalls, food concessions also. I would get in as early as possible and leave late as possible as we didn't have enough time to do the biking trails around the island as we spent to much time in town. Hyannis High speed ferry rates are cheaper during the weekdays.

Hope this helps
Have fun! :C
Mike