Cheers Seemore, I find the kids always have more fun if kids the same age are riding as well. I went by myself to Rusutsu last year, had fantastic conditions and the family got jealous so I'm bring them this year.
Most of Nozawa's onsens are public and free to use. Very basic- though incredibly relaxing. These are generally different to the onsens in the Ryokans which tend to be quite luxurious.