Indoctrination is not encouraging children to explore reality, encouraging them to pay attention to experts while also not relying on someone purely on grounds of authority.
I can't say for sure what these camps are like since I've barely investigated them, but from what I have heard these are quite different creatures than those we would accuse of being religious indoctrination camps. After all - how often would a Christian 'indoctrination-type' camp invite a Muslim to talk about their beliefs?
I wouldn't send my kids - if I had any - to a camp to learn about humanism, or philosophy unless they asked to go there. I may point out that such camps exist if I felt my child(ren) might be interested.
Any children I have will naturally learn, and be taught about thinking, different approaches to thinking - possible problems with certain modes of thinking, and be taught to keep a watchful eye on their own ideas and beliefs lest they lead to problems or errors. If they want to meet up with like minded kids at a camp then so be it.
Camp Quest FAQ
Is this "atheism gone mad" or a valid attempt to counteract the faith based thinking of many schools? Is it a rational response?
As far as I can tell, neither. It is a camp with an academic and philosophical slant. It looks like Scouts only without the enforced oath of allegiance to the Queen and God and one's country and instead with discussion of humanism, philosophy, epistemology and morality. It has the potential to go horribly in the wrong direction, of course, but in and of itself it isn't a big problem anymore than the Scouts is necessarily problematic (though it has certainly gone down some dodgy paths).
One of the criticism thrown at atheists - a fundamental failing of their 'philosophy' is touted as being the lack of community. While creating a community can result in its own problems, I certainly celebrate these initiatives to do that very thing.
If the kids are forced to stand up and declare "I promise to believe that there is no God and the Queen is merely a traditionalist figurehead relic from an outdated mode of government", then we have a problem. If they teach kids about non supernatural methods of knowing and morality - I wouldn't necessarily call that indoctrination.