Austrailian Sheperd Dog Nipping

[Lisak]

My close friend has a 8-9 month old Austrailian Sheperd. We spend a lot of time at her house with friends and all our kids. The problem is that her Austrailian Sheperd is constantly nipping everyone in the behind as they walk around, especially the kids. She says that he is just herding....which I believe is true, but his nipping/biting is causing injury in the form of open wounds and ruining clothes. My 6 yer old son got a wound from this the other day that was bad enough to make him cry and I needed to clean and bandage it. I have done standard dog training and we have a well behaved dog ourselves. So I have grabbed this friend's dog's nose and hold it tight and say "no bite", but as a group, all of our friends are wondering what we can all consistently do together to get him to stop this horrible behavior. Unfortunately, our friend is not taking this seriously nor she is trying to find a solution to this problem. Are there any ideas that I can teach all of our friends to do so that we can train this dog to stop this habit.