There are a number of ways kids classes differ. In an adult class, MA are fun, but they are work. In kids class, you have to have a heavy emphasis on play.
First, you need lots of short duration activities. Let's face it, kids that young don't tend to have the attention span.
Some contests are good. Match them up by weight and give each the end of a belt, and see who can get the other to lift a leg off the floor. Same thing with a staff. Sumo is really good. Who can push whom out of a circle.
Buy some spongy balls and have them toss them at each other and see if they can dodge them, hit them or kick them. Or buy some nerf guns, have a child close their eyes and someone with the nerf gun lines up somewhere behind, about 5 feet away. You count to open the eyes, and then the person shoots the nerf, and the student has to turn, dodge, hit or kick. If it overwhelms the student, you can always have the shooter count to one or two before shooting.
In some adult classes, techniques will be practiced and everyone freezes during corrections. This is a sure way to lose kids' attention. Better to keep the count going when you are making corrections. Even with kids, you can always have one lead the count. In fact, I would encourage you to try hard to get the kids to lead whenever possible. Once they know how to count, they should rotate through the counting on all techniques where you count. And you can rotate them up in front of the room to count. They really like this.
And if you are not yet a parent, and haven't worked with kids, you should know that they really benefit from lots of positive feedback. The old school tough guy stuff doesn't work. Give them a ton of praise. This is as important with movements as with words. One thing I love to watch is kids learning sweeps. It is always fun to watch some 40 lb. tyke take down some 200 lb. blackbelt with a light tap to the calf. Or if you are holding a shield that they are kicking, you can make it look like the kick is knocking you back more than it is.
If your system is strictly standup, you probably want to include some judo-like grappling activities. Simple, gentle throws are all that are needed. And don't forget escapes from grabs. (Ones with both hands are effective.) Parents love to see their kids learning those. Not only is it good self-defense, but it can't be misused on the playground.
Here's one last thing. My apologies if it seems a little calculating. Kids will be most influenced by the last thing that happened in class. If they had a bad day, but had a great last 10 minutes, they are likely to tell that to their parents when they get picked up. So if you want to keep the retention rate up, try to schedule your activities so there is always one good fun one right at the end.
