Hello! I enjoyed your post---I am actually in a VERY similar situation as you, except I've already been a nurse for years, and I started in pediatrics. I have also considered preschool teaching in the future! Oh, how awesome it would be to work with children who aren't sick, who I don't have to poke with needles, etc!!!
There are other things you could consider---
*Any chance you could work in a preschool while in nursing school and see if you like it? I've also volunteered at a shelter for children---maybe you could look into that?
* Becoming a school nurse once you get your RN....(I've heard *some* states require a BSN, and in other states, they hire LPNs). (although this may be older ages and you mentioned preschool specifically)
* You can also get training to be a "paraprofessional" in an elementary school; I don't think there is a degree required. (Again, not preschool age).
*If income isn't an issue for you, preschool teachers make probably a third (or less? ) than a nurse; however, you could move up to become a Master Teacher, or a Director of a preschool.
*Another career I know VERY little about is what is called a "Child Life Specialist"----I've seen that position advertised in Children's Hospitals.