Thx for the link.
Perhaps you should get in with the powers that be at the school? I'd imagine they need volunteers on the day. The more they realise parents are happy to do this on the day, the more likely they'd be to promote it. (Also, a bit of friendly badgering can hopefully go a long way).
FWIW, Thing1's kinder breakup is tomorrow. Another class is having it today. The theme is 'Bicycles'. There were HEAPS of bikes - I counted 12 (and they also have a few runbikes and scooters for general use in their playground).http://www.flickr.com/photos/baudman/4461214492/
(Two bikes in the foreground, a runbike in the distance, and there was about a dozen around the corner).