The best way with the use of which you can get rid of field mice is to use carbonated soda. What you are required to do is to have sweet, carbonated soda in an utensil and place it at the place where you think that mice drink the soda. When the mice drink the soda the carbonization of it will kill the mice and with the use of it your children will also be safe. If you use any kind of poison it is certainly detrimental to the health of kids that are living in your house or even if you have no kids they can come from neighbourhood as a field always attracts kids.

If you want you can use poison also to get rid of them and also some kind of traps but what I have suggested to you is the safest I have found. If you find something safer than this you are also welcome to share your views.