Childcare collective?

I live in South Slope / Greenwood Heights, have a 16-month old son and have been looking for part time daycare. Ideally, I'd like to find two or three other moms who would like to share the cost of hiring a care provider for our children for 3 days. 2 of those days could be spent in our apartment - which is very spacious and includes a large and shady backyard - and a third day where I or another parent would partner with the care provider to take the kids to prospect park, or the children's museum, or the beach, or some other outing. Any parents who would be interested in something like this? I have found some traditional daycares that seem fine, but would love to have my son go on weekly outings with other children. I only work 3 days / week, and would like to be involved.