I think this may be a bit different.
Since you are not all that committed, and you are not interested in preaching to them, and you don't seem to want to play with them, try this:
The next time you meet them, ask them to tell you one significant thing that the JWs teach that they disagree with. I think they will either state that agree with everything, or they will give you some simplistic answer. By simplistic answer, I speaking of the kind of answer one might give at a job interview when asked to 'state something negative about yourswelf.'
If they say they agree with everything the society teaches, then you know they are either lying, or you have some boring automaton that will add nothing to the discussion.
If they pick something that they disagree with, and it seems like a significant topic, then I think you are in for a pretty intersting conversation. If this happens, I will envy you. I would love to have such a conversation with a dubbie.