My town has a Time Bank club where you can help ohers and bank time getting assistance at your place.
You could get more info. Via
facebook. "Ferndale time bank."
We are also members of a co-op preschool which has an auxilliary child care swap opportunities. All parents go through protective services checks and the child care is by a friend with a child our kids' age.
Your idea sounds interesting too. It seems like you could do better with a group of 5 people rather than an open market time-share sort of thing.