In a very real way you stand between your wife and your daughter. She is very vulnerable to indoctrination from any source, let alone her own mother. That doesn't mean you should attempt to indoctrinate her first; that's just as bad. It simply means that you need to be the voice of skepticism in any conversations about Ba'hai, or any other belief. It sounds like nobody else will be.
Of course you can't be there every moment. However if your wife privately tells your daughter things about the faith that would not convince you, firstly she's picking the easier target and secondly she knows on some level that her reasons are not sound, and is using them to preach anyway. Both are dishonest, and she needs to realise that. Her first act as an evangelist should be to convert you, not your daughter.
Pay attention to your daughter, that's the main thing. If you think she's not thinking about something the right way, it's your job to put her straight. That's just one of the things you do generally as a father; this is no different.
Though you have every reason to be concerned, don't worry too much. What probably started me on the road to doubt was the simple fact that my father, someone I respected and looked up to, did not buy into religious belief like everyone else (it seemed). He only bothered to tell me he was an atheist about once. Your mere presence as an unbeliever may well influence your daughter greatly.
As simple as it looks, this witnessing method often works wonders for Ray Comfort and those who learn from him, especially on subjects unfamiliar with this kind of thinking. The Way of the Master radio and TV shows have disseminated this method far and wide, such that especially if you live in the US you're more likely to get this from an evangelist than any other approach.
Let's look at the intended delivery and effect in detail.
1. Would you consider yourself a good person?
If yes, sets up the subject for disappointment and shock when it's later explained that this is unimportant because the subject has sinned. If no, reveals that the subject probably has poor self-esteem and will react well to a chance at redemption.
2. Do you think you have kept the Ten Commandments?
The witness must obtain a no. If the subject does not volunteer any sins, the witness often invokes Matthew 5:28 - "...anyone who looks at a woman lustfully has already committed adultery with her in his heart." Therefore if you've got working eyes and hormones, you've broken the seventh Commandment. In the unlikely event that the subject is entirely innocent, the witness invokes the inescapable blemish of Original Sin.
3. If God judges you by the 10 Commandments on the Day of Judgment, will you be innocent or guilty?
Since the answer to 2 was no, the answer to this must be guilty.
4. Based on that, would you go to Heaven or Hell?
Does that concern you?
The answer to this is unimportant. Up to this point, the exchange has been an intellectual exercise. The suddenly personal nature and immediacy of the final question triggers an emotional response. Any latent belief the subject may have bubbles to the surface and creates fear. After that, it's just a matter of telling the subject that there's only one way to Heaven: to accept Jesus Christ as personal lord and saviour. It becomes the way out of the fear, and is accepted on that emotional level it needs in order to stick.
Obviously, the questions are rigged to produce the expected answers. You will also have noticed that the questions simply assume the existence of God, Jesus, the Ten Commandments (therefore Moses), sin, Heaven and Hell.
Their purpose is not to convince the subject that God exists, but to capitalise on the fact that most people already believe, even if they do not act upon that belief or have not thought about it lately. It prompts a renewed commitment without inspiring new doubt. After this commitment, doubt is even less likely. It takes moderately religious or even barely religious people, and makes them want to be saved.
The spanner in the works is the very thing the method seeks to avoid: doubt. The existence of God, sin, Hell and the basic truth of the Bible are critical premises. If the subject expresses doubt during the initial questions, a common response by the witness is to proceed hypothetically and then invoke Pascal's Wager, e.g. "If I'm right, then you're going to Hell unless you commit to Christ. Are you sure you want to take that chance?"
If that doesn't work (for example if the subject has one of these responses to the Wager), the method is finally derailed and the witness must use other apologetic to bring the subject up to the necessary level of belief.
Without pre-existing fear of God and eternal damnation, the method has no emotional punch. If the witness is in a public place or is trying to "save" many people, he/she will probably decide at this point that the subject isn't worth the effort, hand out a card or pamphlet and move on.
A nice thing you can say about WOTM's method is that it takes evangelical belief to its logical conclusion. If you believe deep down that this stuff is true, it shows you the thing you need to do. However, that is one huge if.
It only works properly in an atmosphere where its premises are unchallenged, so that's where to attack it if a friend or family member has been or is being swayed. Make use of doubt. Get people outside of the little box in which the questions force them to think.
Painful as it might be, and whether you're against WOTM or not, try watching witnessing clips from the WOTM television show on YouTube (or even GodTube). Take note of the level of belief subjects begin with, and how much they're willing to accept without argument before the "punch" line. Witness for yourself the persuasive power of passive belief, and understand why so many atheists want people to shed even this.