In general GSD's seem to be great with children.
I had an experience the other month that really surprised me, we were sat in a pub beer garden which was quite busy there was a couple with a young boy about 2 to 3 years old sat not far away. He was desperate to come over and meet Lucy so his mum asked if (he) was friendly lol, and came over to fuss her. She did everythig right got down to the childs level held his hand in hers and stroked her the correct way no prodding etc, not that she would of minded, he loved it.
Anyway about 10 minutes later the boy was toddling about with his football and his dad went running over doing the old monster routine, swiped him up growling and pretending to eat him. Lucy went absolutely ballistic, nearly pulled me off the bench to protect him! I was shocked she had only known him for 2 minutes, I think she may have changed the views of a few people on the GSD that day..