So disgusted

I have a 22 month old and a three week old. We have been living in our house for almost two years and never had a problem with bugs or rodents but now all of a sudden we have mice. I've never had any mice before and I'm not sure how they get in. I am so worried about catching something bad from them or if that's even possible lol I just always think the worst. We got some rat poison that you put in little houses and I heard them eating it last night but I don't know if that is enough?? Anyone else deal with mice with young children?