Neighborhood kid conflict

I have a question regarding what I think is an over reaction from a neighborhood mom and dad.

The situation is this.
They have two boys. One is 8 and the other is 5. My son is 8 and goes to school with the older boy. They are in the same class. Ever since we moved into our house they have picked on my son. Last summer it got so bad that my son would not leave our house because they would wait for him with high powered water guns and shoot at his face. He's been injured twice from water in the eye and another incident with the younger boy putting a stick through the spoke of his bicycle while riding causing my son to fall and be injured. These kids have never apologized to my son for hurting him.

Fast forward and this neighbor called me on the phone two days ago and says that her boys said my son went after them with a shovel. We don't own a shovel but I did talk to my son about what happened. He was being picked on again by the younger brother and so went into our garage and took my small herb garden trowel. He threatened her boys with it and said a swear word.

I had my son apologize to her boys in front of her and he was punished for the bad behavior. That night my husband receives an email letting us know that they do not want their kids to play with my son ever again. Keep in mind they live three doors down from us. There was a nasty remark directed at me in the letter as well. We emailed them back saying we would respect their wishes and not have our son play at their house but asked that they keep their kids from teasing and shooting guns at him when he walks by their house.

They responded that they feel my sons behavior is too dangerous to ignore and hence have asked us to have our son not play with any of the other neighborhood kids when their kids are playing first. Meaning that first come first serve. If my kid is playing with so and so then her kids stay home. If her kids are playing with so and so then my kids stays home. With a small block of boys and summer approaching I find it insane to make such a demand.

First off I think it's unreasonable to for her to ask other parents in the neighborhood to send my child home if her kids are there first. She has threatened to do this if we don't comply. What kind of person tries to involve other parents to ostracize someone else’s child? This isn't their problem it's her problem. Even our conflicting boys were talking yesterday as nothing had happened. Her and her husband don't seem to get that kids forgive eachother but she is making a point to them not to.

Help any suggestions? Should I notify the other parents in the neighborhood what happened before she calls them or should I let her spread her gossip and look odd by making this demand of them? If I speak to the other parents first I'm afraid I'll look like the gossiper but if she gets their first maybe they would believe her or feel they should comply.

Goldenhair