Live-in nanny here, who has trained a dog and dealt with a high needs child at the same time. If they sprang the dog on you, OP, with no notice, that's completely unacceptable. If they expect you to train the dog without offering more pay AND asking if you want to do it (and are confident that you can do it correctly!), that's not acceptable either. GSs are great, but it's a working breed. They are highly intelligent, the US version is more aggressive, and they are highly active. It's not a breed to leave in the house alone untrained, and it's not a breed that is safe to have untrained around a child. A GS can be trained to pull a child in a wagon or sled, carry water bottles in a vest on a hike, act as bodyguard to an autistic child to keep the child safe and where they are supposed to be, or to do tons of different things. BUT they HAVE to be trained. An untrained GS assumes quickly that they are the Alpha in the family, and puppy nips will turn to disciplinary nips and then bites. GSs have also been bred to savage the wound and not want to let go once they bite, which makes them even more dangerous. While I wouldn't have an issue training a GS (I've had three throughout my lifetime, and I've trained 7 more), you couldn't pay me enough to be around a GS who wasn't being trained at all.