It was a matter of time with mice

For the last 2 weeks we have been leaving the coop door open since the weather has been warmer. It's alot easier on us since we don't have to go back at dusk and close it up. Today, I noticed mice poo in their feeder that is inside their coop. ARG! Their outside feeder is brought in daily. I am assuming the enclosed run is not mice proof as they are probably squeezing through the chicken wire. Any suggestions? I will start closing the coop door again. However, there is chicken wire covering the vents at the roof line. I was thinking of putting mouse traps at it's entry.