I have two young OEGB cockerels that chase ping-pong balls around. You'd probably need bigger balls for Aussies, but the concept is the same. I've also dangled old cds, computer discs and even an aluminum pie pan for them to peck. A mirror can work wonders, too.maybe put some things to amuse them - distract them from pecking.
And the cabbage is a great idea. Just make sure you hang around for a bit, because once they figure out that the big, green dangly thing doesn't eat chickens, it's awfully fun to watch!