My first time on the back of a bike I couldn't have been more than 4 or 5, my Dad let me ride around the block on the back of the next door neighbor's Harley. No kids.....I know my Father was a huge fan of the school of hard knocks, so basically if he didn't think that I would instantly kill myself I could at least take a whirl at it. The rest, I don't have kids so I can't really relate. I know I used to have a neighbor that had 5 kids. So when I first moved in I had the bikes out in the driveway doing some maintenance and was nearly instantly surrounded. They wanted to ride so I made them get them Mother, she didn't have an issue with it so I ended up spending most of the afternoon wrapping kids up in spare gear and riding them around the neighborhood. Caveat being that it wasn't like I was going out on a main road, and I doubt that I got passed 25mph. Riding in traffic....I wouldn't with someone else's kids, its simply not worth the risk. With my own who knows, if they are old enough to ask to want to go along I would probably go along with it. I wouldn't be pushing them onto the bike.