I only care for infants and toddlers aswell, my only rule is that I only care for one "non-walker" at a time. I think that every provider has their age preferences. I for one find that it is easier careing for a closer age group that way our activities can be tailored to their needs. I think that playfelt hit the nail on the head when she said...

It isn't so much about the age of the children as it is the attitude and abilities of the caregiver.

and...

Children close in age learn and thrive off of each other and it is easier than with a spread out age range.