You seem, to me, to be suffering from the delusion that your wife belongs to a group of harmless loonies.
I guess that is just me feeling sorry for my wife. I mean, in spite of the fear that I have of the cult, I still think the people there are overall nice and are generally trying to lead a decent moral life. At least the ones I've met. Still though, I do want to show her another way and not necessarily through church. While I think a belief in God can be beneficial, I also know how it can be abused.
Remember, I've been in a legalistic church before where the preacher gets carried away and tells people how to lead their lives by saying things that go beyond the Bible.
As a child of the cult, I wish I had been protected from the lunacy. Instead, I was encouraged to join it by parents that had access to information that identified Rutherford's cult as a bunch of loonies and ignored it.
Really, what information did your parents possess?
If she joins you in your beliefs, will she think the same of her mother?
NO, absolutely not. Not if I have anything to do with it. If anything, she will think like I do in that my wife (her mom) is a dear sweet person who truly loves God and wants to please Him. However, this spiritual need of hers is being misguided by the machine that is the Watchtower Society. It is the machine that is evil, not the people. If any church I attend says otherwise, I will certainly correct them and I doubt I will be attending it much longer.
She has my sympathy.
She also has your influence, at least in a small way. You see, I purchased that book you recommended to others, "Teach Your Child How to Think." I agree in that we all need to know this valuable skill as I too was in a very legalistic religion and had to break free. I will teach my child that it is perfectly okay, and in fact encouraged, to critically examine my beliefs and her mom's beliefs as I will be doing the same. Personally, I don't think everything is as black and white as so many 'religious' people tend to make them out to be.