The ski slopes were full so we tried Tony's Tube World -- which looks pretty lame from the road, but it is really fun.
You are able to get up to speeds of 25 mph -- the hills are steep and you can even catch air on these tubes.
Even though it seems fun to hit the bags at the bottom, drag you feet to slow down. If you hit them the wrong way, it really can hurt -- jam your neck or back.
My kids 7 and 9 both loved it too. But get there early - they sell out quickly. We were there at 1:00 and they were booked until 6:00 that night.
(You pay for 2 hours at a time.)
Loads of fun for $20 bucks!