My wife is a theist, and I am an atheist. Her family and mine consist entirely of theists with the exception of myself and a cousin of mine who lives far away. My wife would like to take our children to a Christian church I attended for several years. It is a fundamentalist church with a significant number of strange rules such as 'standards' that members not own or watch a television (though this has in recent years fallen by the wayside); that members not wear wedding rings (especially if they intend to be members of the choir, orchestra, or Sunday School teachers); and that members refrain from theatergoing or dancing.
I had decided to concede and consent to allow my wife to take our children with her to church occassionally (since she only attends occasionally herself, often with a certain friend). However, I realized that in so doing I would be allowing my children to be exposed to the message that: they are sinful creatures that need to repent; there are people who know and understand the will of a divine creator; and anyone who does not adhere to the doctrines of Christianity in general and this church in particular are destined for hellfire.
I would prefer that my children are not exposed to these beliefs because they could potentially undermine their own self-esteem and drive a wedge between them and myself as their father. Here is some of what they believe in the church:

