It would be nice to use things such as wii-remote inside of the dragon mouth that tracks an IR led attached to a small dragon ball. The ball should be cheap since it has almost no electronics inside. You can pass one to kids in the crowd and show them how to attract the dragon. Let them play it and keep it, certainly with your hackerspace contact info on it
Don't know how difficult it would be.
BTW, some POV texts on moving platforms will attract lots of kids too. I made one for teaching and smaller kids love it. Again a good piece to occasionally broadcast your advertisement mixed with blessings of spring festival or something while you parade at night.