Your kids kick her, and you smack her and she growls at you? I would growl at you too! Goodness! I suspect that this dog isn't angry, it's scared. I'd say you shoulda been responsible for the life you brought into your home and train yourself and your kids on how to handle a 100+lb working dog before you get one... But since what's done is done, the next best thing you can do is see a professional trainer that can work with problem dogs, and take your kids along too if you can. And take the min-pin too! Your big dog could be picking up bad habits that you haven't noticed from your min-pin because it's just too small to do anything. Small problems in a small dog become BIG problems in a BIG dog.
Look, I have a dog who guards, and you can get past it and manage it, it's NOT an insurmountable problem by any means. But not if people are treating this dog with that level of aggression. It's going to respond in kind. I don't care if it's only a gentle thump that stings a little, if someone decides to escalate, guess who's gonna win? You gotta get the dog to respect you without violence because in a contest of violence, dog wins. It sounds like she's got the potential to be a very good dog. But not without training.
A good dog trainer trains the people more than the dog. Look for that.
I will also note, she's a puppy, an LGD at that. She needs things to do. The first thing you can do as a stop-gap to training is go on a run and play hard with this dog every day. Give her somewhere to run and dig. Is she chewing your shoes? Time to chew on a bone in a crate. Is she eating trash? Time to work on a puzzle toy for dinner, etc. A tired dog is a good dog. She's gonna be a puppy til she's about 2 years old, so be ready for that.
Sorry if I sound salty/harsh but this just grinds my gears. :T That dog is alive and probably has no healthy outlets for it's frustrations. It's up to you to give it some. You shouldn't just get a dog that you don't know how to handle. It's just irresponsible.