Why would a 5k be completely inappropriate for a 5 year old? We just ran a local 5k yesterday, with our 6 and 8 year olds. I checked the results just now and there were: seven 5 year olds, two 4 year olds, and one 3 year old that completed it. It was very much a family event, and we had fun. My 6 year old didn't run the whole thing and I was the lucky adult who stayed with her the whole time while my husband actually got to run with the 8 year old, but I think it was a really good, healthy way to be together as a family. We have two more planned for next year with the kids. We do live in a pretty active community and their school does a running club, so the kids are not entirely new to running. I think as long as you build up to it and it's fun for your kid, then there's nothing wrong with it. Surely it's better to get the kids into running than sitting around on video games all day, right?