This is my advice. You need to keep your dogs under voice control and brush up their obedience. As soon as they or you see a small dog you need to call them back to you, work them to get their attention off the small dogs. It is irresponsible to allow or give them the opportunity to traumatize small dogs and their owners. This gives the GSD and Dobie a bad reputation. You can end up with stiff fines from dog control as well.
Deja, GSD, sable WL, female, born 11 / 2013
Cam, Rough Collie, sable, male, born 8/2015