Help with "non-aggressive" adult aussie biting.

UPDATE I came here asking for insight and advice. I raised putting him down because I don't feel like it he is safe to have around my children, and I am not aware of any person or organization that would accept him with his condition...putting him down was the only option I could think of to remove him from our home. Which is why I asked here to see if there were other options. Based on the unhelpful and critical responses I've gotten so far, I regret posting. Not because I now feel bad, but because I've received no valuable advice.

We have an Australian Shepherd that is several years old. He is a loud barker and charges new people but NEVER bites in these situations. He has exhibited herding instincts by nipping at my wife and I as well as our kids if people are being rowdy and yelling.

These situations have increased in frequency and he has begun the nipping/biting if he is being guided by his collar. He just got me and I immediately pinned him on his back and held his muzzle, he made no attempts to fight and when I released him he was affectionate and normal. But as soon as I started guiding him again he struck out. I was able to close his muzzle and walk him back into our fenced in yard. I leashed him and he would excitedly follow but then snap a couple times if he sensed the leash.

I say it is "non-aggressive" because he shows no aggressive signs (hackles, growling etc) other than the snapping/biting.

It has happened enough times that I can no longer justify keeping him, I absolutely do not want to put him down but suspect that might be the only option. I would appreciate any advice/insight.