For the mansions we took one of the trolly tours. The transit center was a short walk from the through tender port. Bought a ticket there. It was either 3 or 4 hours. Afterwards do the cliff walk. There is also a bus you can hop on and off for DIY. I liked getting the tour with the guide telling me about the mansions. No need to rent a car. Your post should be moved to the Canada/New England board. Scroll through that board there and you will find info.