I've decided I'm going to be as positive as possible, and have no need to bring up WTS stuff. But...if they want to go there, I will have ready for them two copies of the letter I have been writing for (guess how long?) two years and two months. It's presently 29 pages. Yes, I know they may not read it--or even accept it. But I will at least try to reach them with one of the opening paragraphs and two scriptures...
I like the first part of your intention. The second part....well....here is my opinion.
Your family in all probability WILL bring up your stance with the WTS. If you start telling them what you know, how you feel, hand them a letter, etc., I think you know how far that will go. I was in their shoes a few years back. I am almost sixty years old now, sadder and wiser.
I can tell you, as a mother, that if you DO NOT go there, but refuse to, and just keep telling mom and dad that you love them, you will get farther. Before you tune ME out, know that your parents will not live forever.
My father died three years ago, and my mother last month. They were not JWs, instead opposed. I know your situation is the opposite, but which ever way it is, just thank your parents for seeing you. In the coming years you will know that you did all you could- instead of aggravating the situation, to show them the unconditional love that you would like in return from them. I promise you, your mother is not made of stone, and it will cut her to the heart. Anything else, they will take as an attack on their beliefs.
Then, if they still do not want to see you again, you will know that you had nothing to do with it. I promise you in the end you must feel at peace with yourself, and will be glad that you did NOT "have to have the last word."