Elias

He was both smart and stupid. Smart, because he was right about hiding in the cargo hold. Stupid, for not listening to his mother.

Also, while he made some ridiculously annoying decisions (as is typical of a child), he did manage to bring his mother's humanity back on several occasions, which allowed them to make it as far as they did.

Yes, because any other kid that age, in such a situation wouldn't make any mistakes. In reality, he'd probably just curl up in a fetal position.

Yeah, but the Elias's dad was murdered before he could know him, and his mom was never home to raise him properly. So, him being that way, was part of the written character. Actually, on another level, this movie is sorta a metaphor for today when the hoe wife divorces her husband, moves onto the next man, and lets the TV raise the child. These women are sorta like "resource vampires" sucking energy out of their victims until they are bled dry, and the children mostly end up like Elias. They'd actually be better off blowing up their vampire mom, and being raised by a man, even if he is a complete stranger.

What? The kid was the hero. Kept his mom from making stupid mistakes. Most of the time.