Get a black Labrador Retriever. The breed looks menacing but has a better disposition. Get an invisible fence to train the dog to stay in the boundaries of your property.
What dog you get depends on your local (weather), family members, yard size, inside or outside dog, what you want the dog for, barker, or silent but deadly etc.
I decided on a
smooth haired Collie (same breed but with hair like a German Shepherd), because I have a friend with 15 grandchildren on his 80 acre farm, and their rough haired Collie was like an uncle to the children, taking care of them. I had 4 children (now five) under the age of 6 when I got the dog.
I'm on 5 acres, and needed a dog to keep out the Black Bears, snakes and other animals, out of the property. The dog obviously is a farm dog with a purpose, and he is an outside dog. I bring him into the garage and he sleeps in his cage, we don't allow him in the house. My wife has enough trouble keeping the house clean with 5 children.
I studied many breeds and went eliminating them for one reason or another mostly because how they are with children. I ended up with this short haired Collie, rather that a long haired one (called a Rough Collie) because I'm in Florida (heat), and also that long hair on a Rough looks like a lot of work. Collies naturally don't smell. Combine the short hair, no smell, and outside dog that likes to be outside, and the natural sheep guarding instincts, and you have a low maintenance dog that takes care of the children. They are barkers! They will alert you to anything unsusual, they are calling you to come see if something is OK with you. Once you go look and let him know it's Ok, they'll stop (not always the first time). Excellent watchdogs. They are capable of defending the family, and they are scared of NOTHING, at least mine isn't. By the way, they don't drool at all. Short snout dogs drool all over. My dog is an intack male, not castrated, because I want him to retain some aggresiveness.
My dog is not the smartest, but he is extremely obedient. You call him from whatever place 600 feet away, and he comes. You yell at him to stop/sit when he is running right toward an alligator (for instance) which he does not see, and he'll stop on a dime. He was very easy to train, yet, like I said, he's not that smart. On a scale of 1- 10, I'd say he's a 5. If the breed is this obedient with only a 5 IQ, I'd like to see one with an 8 or more.
If you read all the above you'll see that there are many factors personal to your situation.
I did not find the German Shepherds to be trustworthy around children. I never looked at the Doberman because I assumed they would not be good around children. By reading the description of it now, it looks like they are inside the house dogs anyways, which is not good for me.
Here's the link I used to study the different breeds.
http://www.dogbreedinfo.com/collie.htm