Maybe not, but you can do things like:
* Live downtown instead of in a suburb
* Ask your school / DOT to close the street in front of the school during dropoff and pickup hours
* Walk with your kid to school instead of driving them
* Support higher-density development in your area
I grew up in a fairly large and fairly dense (by suburb standards) suburban city of Boston and it was quite walkable as a child (and also had the benefit of having a few MBTA stops). I live in the middle of downtown Boston now and while I find it fantastic as a somewhat immature adult, I wouldn't say it's especially child-friendly.
That being said, I have seen many other suburbs (looking at you, various places in Connecticut) that don't even have sidewalks. That cannot be good for anyone. And Boston certainly has more child-friendly neighborhoods as well.