Actually, you should really avoid ANY strange dog because you don't know how it will behave. I always tell me little cousin to avoid dogs she doesn't know, and if she does come across one and wants to meet it, always politely ask the owner if she can pet it. German shepherds are a very owner-protective breed. While most of them are sweet, lovely animals, some are very feirce when it comes to letting someone near the owner. I know a number of people who were severely mauled by gsheps. I'm not saying its a reason to run in fear and tell your kids that they are mean, but people should be wary with ALL dogs.
I just got attacked by two cairn terriers yesterday. Thank got I had boots on; they ripped up my pants pretty well and it could have been my legs! They were just out roaming loose. They had shock collars on but those things don't work worth a #### if the hair is long or if the dog is really determined to get after something. Luckily I stood my ground and yelled at them until they backed off. I had to actually kick one in the side, which I felt bad about, but they were attacking me. Hopefully they found their way home and their owner will supervise them better outside from now on.