I wonder if that "no noise after 5" thing is bull hockey? I know there are ordinances about noise but they are usually "zero noise that disturbs others" or "no noise after 9 or 10". It just depends on the municiplaity. I would look up the law in your town/county.
I realize that these people have lived there since the dawn of time but that doesn't mean they own the whole block. They bullied you once and I suspect are trying to get by with it again. Even IF they were right all that would happen is a cop would come and tell you to keep it down unless they were busy with real calls. lol I am willing to bet if you told the dog story and brief difficult child story the couple would look like evil boogie men.
You know what is real quiet, a kid carrying a picket sign up and down the sidewalk that says "shhhhh, mean neigbhors". : )
Can you get him a permit of some kind to be a street performer?