I pull my son on a slow, social group ride every Monday evening. It's about 18 miles and usually around 15mph. It's nothing for the frequent riders and somewhat challenging for the new riders. The whole purpose is to bring the community together, but pulling a kid on a trailer turns it into a training session for sure. You're absolutely right there.

I'm hoping it keeps my kid somewhat interested in biking as he grows up, but at minimum, it's a way that allows my wife to ride along with us instead of one of the parents staying at home with the child while the other rides. Good for families!