Ok, fair enough Look... now that I have said my peace about the kids... however you choose to rationalize it.
Now on to the other reasons this is a very bad idea.
What you need to understand about her faith is that it is VERY difficult to be involved with someone who is a member. Do you plan to have children with her? That will complicate things more than you can possible imagine.
The reason why is because a jw carries with them the myth of certainty. They are right! Theirs is the right way! I am sure you can see why this is a very toxic attitude. It taints all interactions with others. You simply are not respected because you are so obviously wrong. There is no compromise with a jw.
Now you or her will likely say "shouldn't a person be absolutely certain in their faith?" No. Because "doubts complete faith, and keep it from becoming fanaticism". The best you can say is your faith has always withstood scrutiny and the light of new facts. But all people are equally capable of being delusional. No matter how smart. No matter how knowledgeable. When a JW clings to their myth of absolute certainty, they are denying this aspect of their humanity. They are saying only you can be delusional. As you can imagine, it makes for a very obnoxious and disrespectful person.
Next you need to understand that the jw is an abusive religion. I don't care or have any problem with what they or anybody else believes. I have a problem with how this religion behaves. Anytime you have people trying to control other people, you are VERY likely going to have an abusive situation. Abuse means that their behavior works to undermine a person's confidence in themselves and their ability to control their own life. They do this so that the group can have more control. The jw is a HIGHLY controlling religion. If all you hope for comes true, your entire life will be wrapped up in someone who is controlled by other people. You will always be second fiddle. Things will be easier in your marriage if you join as well... if that is your bag.
Sorry, you aren't happy in your current marriage. This woman is probably not the answer. If her being a jw was the ONLY thing I would still recommend that you run. I know that isn't what you want to hear. I am married to one and it totally sucks. You can see I am not a bigot, or bitter, or suffering from misplaced anger. I have very legitimate reasons for saying the things I do.
But you asked about the children's spirituality didn't you. Well spirituality in the jw religion is tied inextricably to the religion itself. What I mean to say is they think they are the only right religion. There is no salvation or relationship with God without the religion. The religion is the "way, the truth, and the life, no man comes to the Father but by" them. Frankly, if something helps them to not tie their relationship with God and salvation to imperfect men I would say it is a good thing. A conversation might be preferable method over destroying their family, but that is just my opinion.
Take care Look. I hope you make some good decisions. I hope you see I am not here to give you a bunch of crap. I love you and your family as well as the family of your jw sweety. I just want was is in all of your (but mostly the kid's) best interests. I hope all your choices are consistent with those interests.
CYP