Not sure why you said: Chip was happy and went toward the gate ::: if they were far from the gate and at the beach, but whatever. And btw, I can't walk my dogs here– too many loose dogs. My neighbor walks her chows, but they are BIG chows and at least with her baseball bat, she has a chance. I won't risk it.
I do agree muzzles are not an answer, and the dog simply should not be allowed back. However, if they insist, at least a muzzle gives a little protection so you don't usually end up with a dead dog. I frankly think if your dog needs a muzzle, it shouldn't be at a dog park. However, a dog with a leash AND a muzzle are pretty common and do provide a lot of control when you must take a dog in public.
It sounds like this was a serious wake up call for the family and obviously they care about what happened. That counts, to me, for a whole lot.