They are going to try and get in any way they can. As cute as they are, they breed like crazy. You can't allow them to get a foothold in your house. A mousetrap and some peanut butter got rid of my mice. I guess your cats aren't very good mousers.
Mice are good at getting back into a house if they are released nearby.
I try to pick an area with plenty of hawks and owls. Argonne National Laboratory, Division of Educational Programs, Harold Myron, Ph.D., Division Director.