I don't know how you'd set it up, but I've always thought it would be interesting to do something with kids and this book: http://www.amazon.com/Little-Big-Minds-Marietta-McCarty/dp/B0014E92N2. The book is comprised of chapters each based on a philosopher or philosopy. I can't remember all of them but it includes Plato, Aristotle, John Locke, and Rene DesCarte. I've tried to get my son to read it with me and he refuses.

What I am is good enough, if I would only be it openly. ~Carl Rogers