Coming from my amazing experience of german shepards, with 1 day of it (and 5 visits to the blue cross) I can say it's best to introduce the kids to the dog after the dog gets to know you and have something to distract the GSD incase he/she gets out of hand.

If they're OK with each other then good. If you have young kids, always be in the same room as them and the dog. The more time they spend together, the less threat the GSD will be to you and your family.

As said above, German shepards are loyal and very protective dogs.