There's also a deeper issue - even if there weren't legal and ratings issues to think about, it's still not something most people want to see.
In many violent games, kids are conspicuously missing. As well as Dead Rising 3, recent examples include Grand Theft Auto V and Saint's Row IV. Some games, like Skyrim or Assassin's Creed, have children in them but unlike the adults, you're not able to harm them.
Unbelievably, people do get upset about being denied the right to kill kids in video games. Disturbing, I know. When Skyrim was first released, many gamers felt that not being able to harm children - given that they were able to murder any adult they liked - broke the immersion of the game.
It's understandable that games like Dead Rising 3 and Saint's Row IV avoid these complaints by excluding kids altogether. But I also suspect that for many people - if not most - being able to kill kids would be more disturbing than anything else.
These violent, open-world games revel in their silliness and gore. They're supposed to be funny, with their creative kills and ludicrous animations, but there's just nothing funny or entertaining about killing an innocent child. Even in less silly games like Skyrim, it doesn't seem appropriate - the Dragonborn hero of Skyrim would hardly go around murdering children who mildly annoy them. Surely killing kids would break immersion for you more quickly than the discovery that you can't harm them.
Briefly, I wondered if the interactivity adds something to the mix. You might see kids die on TV, but actually playing through it, killing the kid yourself, that could feel different.
Ultimately, however, I think there are circumstances in which you could kill a child in a game and it wouldn't feel exploitative - if the context were right. There are moments in the hit TV series The Walking Dead where zombie kids are killed, but they're quick deaths and the emotional impact is always important.
In a more serious game like the adventure game adaptation of The Walking Dead, killing a child-zombie would have been treated with the appropriate reverence, and that would have felt bad. But it wouldn't have felt inappropriate or off-putting.
What's more, I think ratings boards would actually be accepting of this kind of character death, even with the added element of interactivity. The deaths of those who are completely innocent should always be treated with respect and should do something to improve the game in some way, such as progressing the narrative or making an emotional impact.
I just don't buy the idea that being able to murder children senselessly could make any game better.
* What do you think about the lack of zombie children? Could killing kids in video games ever be justified? Let us know what you think in the comments below.