How would you feel about a parent who has a young child in the back seat of their car while driving after having a lot to drink -- enough to put the parent well over the "legal limit" of alcohol in their blood to be driving? Do you think it would be right to take away the child from this parent because the parent has shown willful disregard of the child's safety?
I'm not sure I follow your analogy - in one instance there is willful endangerment in the other they probably came to the US illegally so their kid(s) could have a better life. If the only link you're making is the 'legality' or lack of it in both actions then that's a pretty weak argument. What is illegal isn't always morally wrong and vice versa. Maybe I'm misinterpreting your argument; if so then I apologize in advance.