Those aren't the kind of roads that suburbs are made of. Tell them to stay away from those roads. Kids in high density urban areas need to worry about those roads, but this discussion is about the viability of suburbia for children.
And here's a route from a residential street to one of the schools on that map within the same school catchment area: https://www.google.com/maps/dir/39.9349018,-74.9901605/Thoma...
I challenge you to find me a walking route between those two points that does not involve crossing a heavily trafficked road.