How about some good old static electricity experiments?
Some balloon rubbing on hair, or fur on PVC tube, or rubbing their feet on the carpet and shocking each other. Kids love to shock each other.
You could even build a very crude and easy Vandegraaff Generator. There are a lot of DIY ones out there that would be very easy to build and then show to the kids.
While they my have a hard time understanding it as a whole it gets them thinking about what is happening while having fun shocking their friends.