I wish you good luck! This idea is not so far fetched and even exists to a certain degree in Yerushalaim and Bnei Brak. There are places Looking more like alleys or even stairs that have street names. and no cars officially are allowed. Even Emergencv vehicles. (well, they actually don’t fit) Occasionally, some crazy on a motor cycle drives through and down the stairs.
Despite that, you’ll always find people on the busy streets even with kids. But you are right. It is much easier to let kids out to play knowing the car wont come to them. there is a significant distance they must go to reach the street.