If you have the average 2 children with the average ~ 3 years between children, then these concerns are only relevant for roughly 21 years of life. If the average person lives to 80 and becomes an adult at 18, then you have 62 years as an adult. Only about a third of that time is spent caring for your children. That's still 40 years remaining. None of that has to happen on a place with large lot sizes and good schools for the kids, even if you concede that having kids requires large lot sizes and good schools.
Sure and plenty of them live in the city as well. Many of my friends' parents moved back to cities a decade or so ago when my cohort was going to college. I'm merely saying that having kids may increase demand for suburban housing by folks who otherwise would be interested in urban housing, but that doesn't permanently shift demand toward suburban housing.
