SE/Darlene - I'm with you on thinking mice can be cute. I once had a pet mouse (rescued it from a science lab when I was in high school) ...it was so gentle and playful... Then I got to know some little Mickey Mouse mice (great big ears for their tiny bodies, doe eyes...)when a camp counselor because they were residents in our cabins! They can be very endearing, they have friends, wash up much like a kitty cat does, play.....
When it came to my coop, the only thing I was able to live with was rat-proofing - that way I didn't have to hurt anybody. I saw what happened when my neighbors put out poison - cute little mice dead - 2 were lying there dead in a hugging position. They held onto each other at the end. Made me sad. I don't even wish this end on rats who likely feel the same pain and terror but just don't look so cute.
All that said, I know rat proofing is easier said than done for folks with large structures. My coops have been small - maybe 4 x 6 - for only 2-3 birds. So they were easy to rat proof - hardware cloth on the floor and several inches up the walls. Then covered with straw for soft landing :^) I didn't really have any other places they could breach so it was a quick and easy fix. And actually, it was the only thing that really worked anyway. The beauty of it is that it is a permanent solution - you don't have to worry about repeat incidences.... Never saw one again (and there had been quite a few that had decided to take up residence). I strongly recommend this route for those whose setup can accomodate the hardware cloth (the rats tend to eat through the floors or make entry elsewhere near ground level so that's where I put the hardware cloth and they never made entry again).
JJ