Thanks for all of your positive, helpful comments.
I was really leery of the shock collar…seems harsh to me...but it never occurred to me that he might associate the shock with the kids and make him aggressive.
He actually nipped at our 18 month old grand-daughter. She wasn't playing with him...she was walking into another room to see her mom and he chased her and nipped her on the back. I don't think he meant to hurt her...I think that's how he plays. He doesn't draw blood...but it left a welt. We just want to curtail this behavior before one of the kids gets hurt or they become fearful of dogs.
We got him from BRAT and he was one that was found wandering and taken to a shelter in Kansas. We got him with very little info...it just wasn't available. He is very sweet and re-homing him will be our very last option.
We will try the leash and crate or other safe-place while the children are present. He's a very loving dog...I really think he was treated roughly in his former home and that is where this behavior comes from.
We are in Greencastle, Indiana...I know one trainer who works out of our vets office, I'm going to contact her.
I really appreciate all of your comments...I am taking notes and we'll put them into practice. You just fall in love with this little guys and they become part of your family....but you just can't have one family member biting another! Behavior must change!