cimics, that's a tough question- I don't really know what that would look like since being a Christian makes positive assertions (as to God's existence, etc.) and atheism simply makes one negative one (that God does not exist). The assertions Christianity makes carry with them some imperatives for how we ought to live, I don't know that the atheist premise does that.
Copernicus. Sorry if I seemed to imply that atheists
don't do charitable work. Not my intention at all. What a sweeping generalization that would be (and just as likely true of self-identifying Christians)!
Prayers are usually intended to influence God's behavior and attitudes
For many Christians, this makes up the most part of prayer, but I would argue that classical Christianity does not take this view of it. God's behavior and attitudes cannot be influenced- to say so would be to ascribe transitory, human qualities to the Divine. God does not "have" behavior or attitudes to begin with. He is unchangeable, pure act- fully actualized potential. He does nothing but emanate Existence and give being to all things, He does nothing but pour out love, mercy, grace, and good gifts from His infinite store.
The main and ultimate purpose of prayer is to influence the person's attitudes and behavior who is doing the praying, changing him, training his thoughts and perspectives, and making him more receptive to the good gifts that come from the Divine by aligning his very form more perfectly to recieve God's light as he was designed to in the first place.
Finally- I wouldn't ask the atheist to change his beliefs or commit a willful act of self-deception, double-think or anything of the sort. This would just be about actions. The SuperSize me guy didn't make-believe that McDonald's was good during his 30 days, he just went through the actions to learn the effects it would have on him. It was (theoretically) a scientific, curiousity-driven test to see what would happen. The atheist on my "reality show" would approach the 30 days of Christianity in that manner and frame of mind. Does that explanation make it more acceptable?