I believe they are diurnal, but I'd be willing to bet they are out mostly at night when the mice are more active. I'd try f/t like you said and maybe try setting up a warm hide near the f/t . Once you get the snakes out i'd definitely get her working on the mice, snakes are always going to find them.

Good luck, let us know how it goes! And take some pics if you catch any of them. I see you're from McDonough, i'm in Macon.