The reason I like children is more so as a mechanic. Having a customizable unit that you can build to be whatever you want, and also having lots of them, makes the game have more replay ability and options. Even if it's poorly incorporated story wise, the children mechanic adds a lot to the game's replay ability, whether it be building your own units, filling out the support log, etc.
I know a lot of people will say they won't want kids, but in my opinion they're really fun as a mechanic