This is my personal experience with a German Shepard.... He wasn't my choice, a divorce settlement. He is a wonderful compainion, but needs a lot of interaction.  He did come from a reputable breeder. So smart, every event can become a battle of the minds, super possesive (that would be my concern with children) although, I often wonder if a larger pack would suit him better, more to possess, in his dog mind. Protective, but to my suprise, very good with the chickens.  He likes to patrol the length of the run,but they are used to him,  he shows no inclination of agressiveness.  I can go in with the gate opened, and he will not come in.  .  He doesn't shed that much, maybe its just him.  I am sure he can be trained to sweep the table dust, thats how smart he is! 
Sorry about your lab, such a hard decision, but quality of life makes the call.  I do have to say, I am suprised by the doberman comments...(sorry)  I have only met two, and they were kind of wild, even with obedience classes.  Could be the owners.  Our neighbors also had a GSD who lived outside next to the chicken coop, and took good care of the girls.