Using poison is a horrible idea because something will end up eating it. Then whatever ate the mouse/rat will also die from the poison. It's just a cascade effect and not a good one.
Bucket traps work wonders and there are lots of you tube videos on how to make them.
Before you put your girls...
I have black bears where I live. One night I had a momma bear and her babies break into my original coop years ago. The next night they tried again and couldn't get in. Never had another problem with them. They want easy meals and if it takes to much effort they give up.
Where I am if you shoot a dog you have to kill it I do believe. If you shoot to injure it to try to scare it away you could end up with a fine for causing unnecessary suffering to the dog or something like that. Also the dog has to be on your property when you shoot and kill it. Would check to...
For future use of your original coop if you so choose dig a trench around the outside of the coop and nail hardwire mesh to the bottom. Place rock on top of mesh then cover with dirt. I had rats getting in and taking my babies at night. Now no more problems.