I'm in the process of building another coop & I have ALOT of Silkie chicks that NEED to be moved outside. All I have right now is a chicken tractor. I'm going to put a large plastic bin in there...upside down with a hole cut in the side for them to get in....but would it be ok for them to actually sleep on the grass or should I lay something over thr grass? I've never had to do this so I'm unsure. Any ideas? Thanks!