I really endorse the idea of a trial period, or, even better, sending a single parent down on an exploratory mission.
People are very different in their expectations and desires.
Buenos Aires is so big and varied, it can cover a lot of bases, and without knowing a lot more about what YOU want, its hard to know where you would like to live.
I, too, have two boys, although mine are older, but we would never, as a family, have even considered the northern suburbs- we are just not suburban type people, in any city on earth.
When I lived in LA, I lived right in the middle, and in Seattle, as well. My place in Buenos Aires in in Barrio Norte, and I would have no qualms whatsoever having my kids live there.
Its urban, much like friends of mine who are bringing up kids in apartments near central park in NYC.
Tastes vary.
If what you want is a suburban lifestyle, with a lot of time spent in the car, that is certainly available.
I have Argentine friends bringing up kids all over town, in dense and not so dense areas, and know people who grew up all over. None were murdered or kidnapped, they all lived normal childhoods, in many different neighborhoods.
I know a couple from Malaysia who live with their kids right in Palermo Soho, and love it. They can walk to most things, the kids take buses to school, and the subte is nearby. Of course, they also have a car, but they dont use it for everything.