Between working a full time job, going to school full time and being a single father, that's not something that would be easily accomplished either, as much as I would LOVE to do that.
Maybe when I'm done with school and have more free time on my hands to run a business like that it would be something to think about. Plus I don't want to be one of those guys who runs a business and lets somebody else teach all the classes.
I coach little kids and HS wrestling. HS practices are 2 hours and kids are 1 hour. The way I combat the little kids getting lost is several things.
We usually take a good bit of breaks at the end of each technique and we always play some type go wrestling related or motor skill related game at the end of practice.
That's how the kids classes I taught back in Illinois were. We'd warmup for about 15 minutes, do technique practice for about 35 and then play a 10 minute game that was motor skill related.
The kids responded to it very well. They always had fun and always learned a lot. So it's hard for me to comprehend 20-30 minutes being sufficient.
I know karate is looked down upon these days, but I used to take shito ryu with Hanshi Minobu Miki. They always had an incredible kids program, turned the little monsters into polite kids, parents must have loved Miki.