Kids can be killed in film. No question and even with both Alien and Predator franchises, they went there. In the case of film you tend to see that in the more adult material anyways so with less restrictions being on an R-rated property it's not like you have to keep the kid alive, just that a lot of people do.
It's also worth noting that the people over at Darkhorse (at least as far as we know) don't answer to the same people Marvel or DC do. And even then both companies have killed off kids, DC in particular has a string of dead or murdered children. Jason Todd (one of the many Robin) was killed between as an older child or young teenager and while has gotten older since then, it was partially shocking because he was so young. There's also Lian Harper (who pretty definitively was a kid) who is shown to be a victim of a terror attack and we even see the body. Marvel was also noted in a few comic events to show kids actually getting nuked when Nitro exploded leading to Civil War which would then go onto inspire the Captain America movie.
No you can totally kill kids off in comics.
