Join Date: Nov 2012
Location: Albuquerque, NM
I also don't think your girlfriend is overreacting. Biting hard enough to leave marks is very serious, and could easily escalate into a nastier bite. It doesn't matter if he's just doing it in play, which is what it sounds like--a bite is a bite when it comes to damage.
I would recommend hiring a trainer to work with you in person if you have not dealt with this kind of behavior before, just because the stakes are kind of high--if he were to get too excited and actually break skin and injure the child, you could be looking at a kid with permanent scarring, rehoming or euthanizing the dog, maybe breaking up with your girlfriend... That said, it shouldn't be too complicated to teach him manners around kids, but it will require some work.
He should not be loose around the kids ever for the time being. When they are home, he should either be leashed to you or in his crate (or locked in a bedroom or something if he is not crate trained).
What you need to do is teach him how to interact with the kids. This means not letting him strain at the end of the leash or jump up or anything like that, and rewarding him constantly for calmness.
Are the kids old enough to listen if you tell them to stay away from the dog? If not, only have him out when your girlfriend is there to help manage the kids, so you can focus on the dog. Right now I would not let the kids touch or pet the dog at all. Instead, teach Kodak to be calmly in the room with them. Reward him for ignoring them.
Once he can calmly be in the same room with them and mostly ignoring them, then you can start letting them pet him. Make sure everyone is calm (I find these things go best when both kids and dog are worn out, as long as the kids aren't overtired) and teach the kids how to nicely pet the dog. Reward Kodak for calmness, and if he gets excited remove him immediately.
Eventually, he should learn to interact with the kids appropriately and not bite them. I would still keep a close eye on them though, and always be prepared to remove him if they're playing and he starts getting too excited.
The rowdy dogs:
Hector-2 y/o GSD (mix?) rescue
Scooter-12 y/o ACD/Border Collie mix
Bandit-8 y/o ACD
Wooby-14 y/o ACD
Abutiu "Abi"-ACD puppy and hopeful future SAR dog!