I go to a christian camp...

So, I go to this christian camp my grandmother told my parents about, it's about half a mile from my house, quite convenient, though... well, they're christian and I'm an atheist, and I haven't told anyone about it in the last... I think six years I've been there, and I've been beating myself up about it. I made some really good Friends there, and I feel horrible that I've been hiding that from them. They're the most understanding people I've met in my life, but I don't know if I'd be allowed to go back o how they would react, should I tell someone?