@James Jack ...
As many here have suggested over the years, if you want out, maybe it would it be better to just walk away?
If you go the DA route, as suggested, you are playing by their rules. If you walk away, you are the one in charge. It's of course, entirely up to you.
You will annoy them far more by walking away. When they make periodic calls or attempt to visit and ask you the question or two about do you still believe in the Organization or whatever, just say yes. When they ask how they can help you, just say you will give it some thought and come back next year and thank them for their time.
That will be more of an annoyance to them than sending any kind of letter where they can "write you off."
If when they ever chose to return, if you have a friend or neighbor, have them at your home when they come to visit. The whole tone will change. They will have wasted their time since they will not talk to you directly with someone else in the room. When they leave, thank them for visiting.