Okay, problem solved for tonight. I took out one of the inside coop floor panels and put my 7 year old in there. He put the chicks on the roost. LOL But that's probably just a temporary fix.
Here's a solution for you and relatively easy. Enough rat wire to staple to the piece of wood resting on the ground, about 8 - 10 inches wide to go around the base of the coop. Rake away about 4 inches (width) of grass/ground cover. Take long garden/fence staples/sod staples (avail at hardware stores) that are about 4 inches long and peg the wire flush to the ground. Then recover the wire with your ground cover.
I did this with chicken wire to keep my two hounds in my yard (dachshunds love to dig). Diggers hit the wire and it stops them from further digging.
Hope this helps