Hey, here is an idea; why dont you offer a course for the parents, separately? Kind of give them an idea of what you want to go over, sort of as a training class. This way, you can work out the kinks, AND present it in a non-threatening manner, to the ones who have issues with their kids being in harms way (or their perception of harm). Introduce them to the basic tenets of survival, and that it is NOT anti-governement, or anything like that; it is, simply put, being prepared for the unprepared night out (in this case). After all, one would hope that, when little johnny fails to come home from a walk in the woods one night, that he is found the next morning safe in a warm shelter, none the worse for wear. Beats the alternative...
One thing I REALLY liked about my military survival instruction was using the word SURVIVAL as an acronym. You may have to alter some of them a little, as it is military oriented, but, in the end, it can be worked (not sure if you guys used FM 21-76 or not in the corps):
Size up your situation
Undue haste makes waste
Remember where you are
Vanquish fear & panic
Improvise
Value life!
Act like the natives
Learn basic skills

With the exception of acting like the natives, I think that you could touch each subject in a positive manner, and really help people to understand the lessons you are trying to teach.
One last thing; someone else here mentioned setting up a camp, and doing this off to the side, close to camp, within shouting distance. I think that this may be a better idea, as it may be more friendly to those who are opposed to the idea. Your idea of doing the "unplanned" night out is excellent; maybe left to those students who want to learn more, like a sort of advanced course? Just a thought.
Of course, you can always put the parents through the capture/interrogation phase of the survival course