I cannot imagine potty training two kids and a puppy at the same time. I mean what do you do first thing in the morning, take the puppy out, or put the 2 year old on the potty or the 1 year old on the potty? It sounds like an awful lot of running to the bathroom or to the outside. It sounds like being run off your feet.
My brother-in-law wants a dog, but his girls are almost three and 1.5. My sister says no way until the girls are potty trained.
Frankly, raising babies and puppies, well it is just great if you are familiar with owning the breed, but if this is your first puppy, the GSD might not be the best starter-dog. I mean, they can be quite bitey, and they can chew you out of house and home. Yes they do shed. They are smart, they can walk all over you if you let them. They are a breed that was bred for their ability to protect, to herd, and to guard. That means there is an element of prey-drive, aggression, and intelligence/independence bred into these dogs. They should be high energy and have high drive. This means a dog that had better have many outlets for its intelligence, energy, and drive.
With a bunch of kids, some of the babies, some school-aged, well, kids come first. Training and socializing the puppy might fall to the lower third of the list of things we have to do today, and well, if you have a bunch of kids it is even more important that the puppy be trained and socialized.