Oh, I thought you had your tour on Friday. We worked Friday from 9AM-11:30AM from the rotunda down to standing rock. We were actually doing an educational trip in another cave in the park on Saturday. I did come down to the historic entrance around 12:30-2PM to sit and chat with the guides though.
When the tour opens up again, the Grand Avenue tour is one of the best offered at Mammoth Cave.
If you really have some time available, the NSS has a restoration group(which is what we were doing) that has 3 or 4 weekend camps and a week long camp every year. the website for that is
http://www.mcnprestoration.com.
We work on quite a few interesting projects. Hauling old creosote wood out of the river, lint removal, trash clean-up, removing old electrical wires, burying the electrical wires that are being used now to hide them, and many other things.