What I think is that the co-op is primarily for families where the parents have decided to homeschool their children -- that is, they've decided their kids will most likely not be attending kindergarten or elementary school. We aren't just a large scale playgroup. Most of the people in our group have at least one school-aged child (age 4+) and many also have younger toddlers and babies.
It wasn't clear to me from your post whether you intend to homeschool, and whether the other child you take care of will be homeschooled. If so, you're certainly welcome to come to any of our events. Probably the ones most enjoyable for toddlers are park days, trips to the zoo and aquarium, and things like that. We often do those types of outings. The idea is to give our homeschooled kids a chance to make early friendships with other kids who will be homeschooled, as well as some social support for the adults!
There are currently about 50 families registered on this message board, who are receiving weekly updates about our activities. Nowhere near that many families actually come to any given event. We consider it a big crowd to get half a dozen at a time.
Hope this answers your questions.