I've been to several Song Schools. The purpose is definitely to help songwriters with their art/craft. There have not been any "teach the teacher" workshops as far as I know; although, who knows, maybe there will be this year, you may want to check. That said, by participating in the workshops and seeing how the other instructors teach their (adult) classes or workshops, you might be able to pick up some useful tips.
And even if you don't learn anything useful for your profession, you'll be camping out in a beautiful environment with songwriters from all over the US, playing and listening to songs, relaxing, having a few drinks, and making new friends. Not a bad way to spend your time.
You may want to talk to Paul Reisler since you know him and ask his advice. You can also call up Planet Bluegrass and talk to them.
If you decide you want to give up your ticket, there are no doubt people waiting in line to buy it, so you'll be making somebody else very happy. Note that you'll need to sell your ticket back to Planet Bluegrass as opposed to an individual, see the rules posted here on the forum.
Hope that helps.