Turning around Theocratic arguments

Sometimes in engaging Christian friends and trying to talk them out of religion the refrain they spit out when they consider the other side is something like "well what would be the point then, if there is no god everything is just meaningless". Turning that around, which I haven't done in the past, I wonder if the opposite is true. An argument along the lines of "having a omnipotent and omniscient deity watching and ultimately in control of everything, even if there was some facetious modicum of 'free will' (ultimately I can't see how it could be free will if an all powerful source which knows all is ultimately setting everything in motion they would also have to know perfectly well the consequences and how much free will/bad decisions/ good decisions would be exercised - b/c if they couldn't divine that then they wouldn't be omnipotent) means everything is ultimately pre-ordained and since everything is going according to gods plan what does it matter what someone's contribution is?