I'm young enough that most of my field trips required approval of my parents. As long as there is an opt out I don't see the problem. What are you afraid of? That being exposed to an opposing opinion will be too much for your children? That they are not strong enough to be able to see both sides of the issue and MUST only be indoctrinated with beliefs you agree with? BTW: I assume that you have never been to the Creation Museum? I don't agree with everything they present, but I respect their right in a free country to present it AND the right of parents to decide whether or not to allow their children to go there, even if it is on a school organized trip. A mind is like a parachute ... it works best when it is open.