My chicks are a couple of weeks old and they have a blast running around chasing each other with some red clover flowers that I found in the yard. Leave a little bit of the stem on so that they have a "handle to hold onto while they run around with it". The other thing that they have enjoyed was the leafy tops of some strawberries that we ate yesterday.
I gave my chicks a paper towel roll and I cut some of the edges off so that they could play with it. They loved climbing over it and trying to get in it. It was a blast to watch!