The gardens and mansion are a wonderful alternative to the often more crowded Newport mansions. Depending on what time of year you visit, you'll have an opportunity to see some amazing floral displays and specimen trees. The self-guided tour around the expansive grounds is easily managed with the free map and guide. The mansion tour is also self-guided, but docents are available to give you some history of the home and family or you can also learn more from the information cards posted in the individual rooms.
If you are a AAA member, the ticket for bothe garden and mansion is $10.
I went on a Sunday morning (they open at 10), and I practically had the place to myself.