Wow, sorry you're having these issues. Did you sign a contract with the breeder? If so read it and see if they are obligated to take the dog back.
That said I so agree with LavenderRot that if you decide to rehome the dog you should use a very reputable rescue. I would never place a dog with aggression issues on the internet. Even if you tell the people the whole truth about the dog (which most people will not, not saying you won't though) you simply don't know what they will do with the dog. Will it be snake food? Really, who wants to buy your uncontrollable dog??? Why?? And please, do not give the dog away free online!
I'm so sorry you're in this terrible dilema. Make your decision with the best interest of your children first and the dog second. It's so sad for all involved. I have to say you are getting great advice here though.