How to get rid of field mice from a house with a dog, toddler and newborn?

Last night my husband saw a field mouse come in through our gas fireplace. This evening I SWEAR I saw it run behind the toy box. I HAVE to get them out of the house! I have a newborn, a 19 mo old (who leaves her food all over! UGH! Probably why we have them inside), and a dog so I am having serious concerns about using poisons. Also, I am concerned about the fleas that they carry. I noticed a bite on my daughter this morning but her room is far from the living room. Is it possible that this is a solitary mouse or do I have more? Should I put one bite under the house? Would it make a difference or attract more mice? We back right up to a big field so I know they're around. I can't just get a cat because of allergies, I can't set traps because of the dog and kids, and I can't just lay down poison for the same reason... What should I do?