The situation is extremely complicated. It will all depend upon what kind of financial situation she is in. Don't get me wrong but if the guy were financially stable then I don't see the reason why he'd have stayed here illegally ( as you said that he's out of status ). Thus, I'll have to conclude that the chances are pretty slim.If he didn't have a son too then things would've been different but being bluntly truthful, I don't see any ways that the embassy will issue visa to both his spouse and the son.