From what I understand from my teacher friends, is that it's pretty hard to teach early childhood without the certification. School districts just won't hire you without the certification completed (unless they are desperate to have a position filled and you have some good internal connections), and even then, alternative certification is not entirely welcome in an elementary setting (though it's much more accepted in Jr High or high school). Your best bet might be to work in a daycare setting or private school (like Montessori or Primrose -- "daycares" with an educational design and focus) while getting your certification.
That way, when you do get your certification, you will also have had recent, tangible experience in understanding and managing a large group of young children.
Also, as far as teaching groups of young children (the ages you mentioned in your post), the Montessori method is making its way into mainstream/public schools. Educators are learning that a lot of the "montessori ways" are more developmentally appropriate in the younger ages, so some of the tactics are already being employed in public school kindergarten and first grade (though they would not officially be referred to as montessori).
You might want to look into Montessori certification. It may not take as long and you could possibly get a job more quickly.