Some of the stories have children in them, and I think this would be a really cool addition to the game. And no, lalafell are not children :P

But it would definitely be the first MMO to allow you to play as a youngling, and not someone over the age of 18 (even the youngest sliders always imply graphical age +18.)

The Final Fantasy series definitely implies that children are a part. My favorite example is Rydia in [IV], and her storyline as a whole. Honestly that's a pretty great story, because it seems a child is what turns Cecil to no longer want to be a dark knight.