I have not known anybody injured on a professionally run slope. I love tubing. We have a place near here that does skiing, snowboarding, and tubing. They have employees at the top who tell you when it is safe to go down, and they also have their own "mountain" emergency personnel. Since they make sure people are seated correctly and are spaced appropriately I have not seen any accidents.
Now, I did know somebody who died tubing, but it was not at a monitored place. Our college was built on a large hill and our field hockey field was in a giant bowl. It was a popular place to tube, but we weren't supposed to after dark. Nobody followed that rule and security looked the other way. A girl in my class was tubing with some friends. Their tube rotated and she ended up hitting her head on a goal post and died. Now, this was a freak accident. If you are going someplace that is monitored or does not have large obstacles, this will not be a problem.
I think it sounds like a fun party, as long as you use some common sense you will probably be okay.
) I got a serious concussion snow tubing. This was not at a facility, just out on a hill with friends. We had been down the hill several times, and the decided to go down all together holding hands. I'm told my tube hit a ramp/ bump in the snow and the tube and I both went airborne, but didn't come back down together. I landed face first. I had some serious scrapes - one half of my face was stabbed over for a couple of weeks - I spent a few hours in theER getting checked out and I missed a week of school because of the concussion, dizziness and headaches. I was lucky not to have any permanent injuries. If I still lived somewhere that sledding was possible, I think I would let my kids go if it was somewhere professionally managed....
