I have a run 16’ x 32’. Half the roof is solid and the other half is wire. (Lots of prey birds and feral cats around) I’ve been pulling grass and weeds out of the run and covering the base with river sand. I’m wondering if I should just leave half the run full of grass/weeds to let my chicks have some fun. They are 5 1/2 weeks old and seem ready to go outside the 6x8 coop. Will tall grass and weeds be harmful?