So encouraging to hear adultlike behavior concerning the kids from divorced parents! Keep in mind that since she is remarried to a JW ( Did you say that in a previous post?) that the cooperation now might not be so cooperative in the future. You sound very level headed, as does she at this point in time.
A focus on not baptising must be reinforced frequently by you. Having them investigate questions on thier own and then have a discussion later is also very important. Get them to investigate, to read, to research. All critical thinkng skills. 'Also make sure the kids know what they like, what they plan to do, what they want out of life. It could be a fairly regular discussion about goals and how to achievce them, how to vary them when obsiticals arrive, not to give up.
You have the opportunity to provide them with the tools needed to think critically. Such a golden gift for them.