There is already this great thing happening in Brisbane that has very similar principles to PARK(ing) Day. It's called "Living City" and was developed as a collaboration of teachers, local government planners, artists and design professionals. Its goals are to educate and empower young people about the design of democratic and sustainable public spaces, and consider the perceptions of young people about their city and its public spaces.
It has explored some of Brisbane's most important and exciting urban places including Boggo Rd Precinct, Howard Smith Wharves, King George Square, Kelvin Grove Urban Village, Roma Street Parklands.
Just change the word "Living City" and the word "young" (people) and it is PARK(ing) Day!
"The Living City program explores the ways in which young people relate to the city. They don't have to be an "expert" designer or prospective architect or town planner to enjoy the program. The participants need to be curious about how cities work and what makes particular spaces interesting, and to think about fresh, creative ways of making and using city spaces."