I think the biggest question is whether or not there is a sufficiently large base of other kids living nearby and whether or not kids can safely get around.
Cities have their own trade-offs and I'm not quite sure what the best spot is to raise kids after having seen a large range of options, all I see is a mixture of drawbacks and benefits for each.
Right now I live in a 40k people town near a major city. This seems to be a nice optimum: have the big city when you want it, but much better quality of life and more space. I'm not sure my kids would benefit from living more rural or more in a city, but if that changes we'll be happy to move to maximize their chances.