A few years back, in a previous life when I was a Scoutmaster, I had finally talked our Troop into going on a wild cave trip. We went to Laurel Caverns in western Pennsylvania (http://www.laurelcaverns.com/). This is really the ideal first time trip for Scouts to experience a dark cave tour. They supply most of what you need including the guides and the cave. They also have other activities than the dark tour like Climbing and Geology Merit Badge. They also offer a few Girl Scout badges as well.
We took the three hour dark tour. I'm trying to condense all the video into a one or two short glimpse of the tour. By the way, the kids in this video are all grow up adults now.