Speaking in a fan interview on Bethesda's site, Fallout 3 executive producer Todd Howard has said in no uncertain terms that the anticipated RPG won't be one for the kids.
"[The game includes] slavery, children, drugs and addiction more than the others, as those factor for into the setting more," he said in response to a question about mature content. "In regards to nudity and child killings, no, it features neither of those, as they don't really add to the flavor of the game."
Howard added: "You will not be able to be a child killer. There are several reasons for this, some of them are very basic, like we wouldn't be able to sell the game, anywhere to anyone, if the children could be killed. I'm not using that as a scapegoat. We never wanted the game to offer any incentive or desire to be blowing kids away, so from our initial designs, we didn't know how we were going to handle if you shot them, we just knew it was going to be a big no-no, especially with a system like VATS and the graphic fidelity the gore has.
"Anyway, when attacked, all children flee and any regular NPCs friendly to the children will instantly attack you, so it feels good in the game, in that there is an appropriate response."
More through the link.