I had two rescued dogs for about five years that my ex ended up keeping - chow/retriever and chow/husky mixes. Wonderful, loving dogs, but they were runners (picked up full grown) and I didn't devote enough time to training them. I always said that they made me appreciate the things in a dog I would want down the road.

Fast forward to this month and the wife finally agreed that we need a dog in the house for security. I have been talking about this for a while but until recently I couldn't commit to being the one responsible for the dog (walking, etc.). We have young children and the youngest (2) is quite afraid of full grown dogs, so we want to introduce him to a puppy and have it grow up around him. I saw again this weekend he was really afraid of big dogs, but before we commit we will need to have him spend time with a puppy to make sure he doesn't develop a life-long fear of dogs.

So, for me, I need to have a dog that isn't prone to run, that is protective of my family, that is very responsive to training, that needs moderate exercise (walk 15-30m a day, five days a week or so), that can tolerate cold, and is a puppy. I am leaning towards a GSD for many reasons but one is because there are some decent breeders around who could provide us with a good puppy with a known background.

My wife is fairly sold on the idea of getting a puppy from the shelter for humane reasons. I'm trying to explain a breeder gives us a known commodity, good genes, and you stack the deck in your favor in terms of a breed's characteristics. This will be a discussion that will go on for a while I'm guessing.

Am I missing anything here? Poor breed choice? Advice on selling a breeder?

I wouldn't pass up the dogs in a shelter.  Most are there because of the owners behavior, or lack thereof.

Sure, pure bred dogs have specific tendencies, but lots of shelters, or breed specific rescue organizations can find you a dog with the traits you are looking for.  If you have a specific breed in mind like the GSD, look at the GSD rescue organization in your area.

Almost every breed has their own rescue organization.  These are different than the local Humane society, animal control or the ASPCA shelters.

The local rescues have no puppies, and that is a dealbreaker for us unfortunately. If it weren't for that, I would have come home with two Doberman sisters who are at my local shelter.

There are very few breeds which I would consider if I could only exercise the dog 1/2 hour or less per day. Heck, I've got a Neapolitan Mastiff and I still walk her for nearly an hour each day. 20min would be the minimum I would take her out for exercise on a regular basis. Of course I don't know that I would recommend one to you since you have kids. They will have to grow up tough.
 

I know, it's not ideal, I wish I owned a different home with a different kind of yard.  That's why it's important for me to have a dog that doesn't run so I can go out (or the kids can go out) with the dog into the yard.

I would have preferred a Doberman, Rhodesian Ridgeback or a Belgian Malinois personally.  But, the Rhodie wouldn't be good for our situation and the Doberman & Malinois would be impossible to find by us.

look, with that level of exercise you really need to rethink this.  That is just not realistic, nor is the demand for a dog that doesn't run.

Unless you get something like a basset hound, you just don't have the space nor time to have a healthy dog.

Your dog will soon end up at the pound.

I don't think there is a breed of guard dog that doesn't excersise work out.