After getting to see the bus in action, I think it's best suited for the 2+ crowd who will be taught a formal lesson by Michael and Mia from this point forward. (The younger kids can get involved if they have mom on the bus with them during lessontime, though.)
I envision TumbleBus day as a peaceful time for us moms to chat in the shade outside the bus while the kids tumble away to their hearts content.
Each class costs $10 and it is on a drop-in basis. The kids each received a TumbleBus tee shirt after class and some fun stickers and hand stamps.