How much do you weigh?
It is my firm belief that no one over 75lbs should be riding anything lower than a 12 DIN binding in the park. Since most 12 DINs can go as low as 4.5, you'll easily be able to get the right DIN and have a binding that is strong enough to handle park skiing. If I were you I'd look into finding some STH 12s or even 14s (depending on your weight, height, and BSL), they're burly enough to hold up to park skiing, and still super lightweight.
~WAKIN' UP THE NEIGHBORHOOD TONIGHT!~