I did the MS ride here, but it was flat. Also ours is two days, 77 miles each day. Our church group just did the first day only. The thing you might be interested in though is that our church had a group of riders. and several people had a child (11-ish) along. and three members of the youth group went too, teens on hybrid bikes. None of the kids had a lot of experience and they finished the 77 mile ride with the rest of us, slow - (total 8 hrs), and seemed fine. They were all in church and smiling the next day... Unless your ride is hilly, I would think your son would do fine if he rides already.