The Cave of the Winds was actually the high point, saved for the very end. (Plan on getting wet, particularly wet feet.) My daughter (age 11) loved it. The boat ride was also great, as was the stop at Goat Island.
Our tour guide Christine was wonderful: Quite informative, enthusiastic and funny. In addition to her excellent work as our guide, she took us to a great Italian bakery for a quick lunch, and told us where to buy souveneirs without overpaying.
I highly recommend this outfit and this tour guide.