Most poisons available today have no secondary kill factor...meaning, the mouse can have eaten the poison and died from it, but it will not kill the animal that eats the mouse.
Secondly, the dogs digestive system is geared for eating game (think of how many folks feed a raw diet)...I have a few dogs that catch and eat mice, ground squirrels, jack rabbits, birds whatever they can catch....thier systems are capable of breaking whole animals down and being resistant to many diseases...as long as your dogs are healthy, vaccinated, etc. you shouldn't have anything to worry about.