I know there is a post somewhere here about getting rid of a lot of mice, but I don't know where exacty so I'll add-lib...
Take a 5 gallon bucket and fill it 3/4's full with water.
Take an empty soda can and put a hole in the bottom and run a piece of string through it, top to bottom.
Tie the string ends to each side of the 5 gallon bucket (make a hole at each side, or heavy duty tape), so that the can is "suspended" over the water.
Make a "ramp" (a piece of wood or limb) that the mice climb up, up to the edge of the bucket so they can access the string/can.
Cover the water in the 5 gallon bucket with Black Oil Sunflower Seeds (BOSS) to cover/coat the top of the water so it looks like there are only BOSS in the bucket (they float).
The mice will climb the "ramp" and jump on to the can to try to get to the seeds, the can spins and the mouse/mice fall into the bucket and drowns.
Honestly, if you have a lot of mice, this is the only way to get all of them without worrying about your chickens getting hurt from a trap or mistakingly eating poison.
Good luck with your mouse problem, and I'm glad your Dad finally knows you weren't exaggerating!!!