The attention span of your average child isn't quite that of your average adult's. Having a class time of an hour may be too much for some of the kids. Start with either 30 or 45 minute lessons, depending on how they react.
Also, explaining concepts, theories, etc. to children can prove to be difficult, since many of them will not have the understanding that their adult counterparts have. In general, try to think like a child, and explain in terms that are easy for them to understand. It's easier said than done, though, and it takes patience.
Bless your heart for starting up a kids' class. Furthermore, best of luck to you!