You don't need "low rise cohousing communities" to have families in cities. Japanese cities are extremely dense, yet people raise families there just fine. On my trip to Japan, I was really struck by how many children I saw in the middles of cities (moreso in some districts than others, of course), whereas I never see children in downtown American cities.

Of course, Japanese cities don't have enormous parking lots, everyone driving cars, etc. They have taxis of course, and some cars (not a lot really, given the population), and work vehicles, but not the huge amount of vehicle traffic we have. And of course, there's tons of trains and buses, so it's really cheap and easy to get around by public transit. On top of that, there's bicycles: tons of people get around by bicycle, and the traffic level and speeds are low enough to make this very safe, plus there's no culture there of being aggressive towards cyclists or pedestrians the way America has.