Kicking Through Baseball bats!?!

get some balsa wood it will be kinder on your body and look mighty impressive when it splinters

I remember when I was a kid, many many years ago ;-), I trained at Kenny Waltons Tae Kwon Do school in Bradford. We did regular demos at which we would break boards and stuff and people would clap, maybe raise the occasional cheer and we would feel good about ourselves. That was in the mid 80's and everyone has seen it a million times, personally I think thats all a bit old now.

Braking boards or bats doesnt relate to any kind of self protection skill at all. I reckon you will recruit far more students (and the right kind of students) if you demonstrate what your art can do for them in the real world.

Watch the Fist-Foot Way. Great movie. 

second guess the whole demo thing- unless of course you are really just giving people a peek at what the class training sessions are like. 

The most successful demo's I've done are to just simply run a regular class in front of people. No fancy moves, no changes in posture or attitude because 'its a demo'. Just have fun and perform in regular training.