First off, interesting scenario
For argument's sake, I'll agree that we should do it. As to who, would that really matter? Anyone, child or elder, saint or crook, no matter their personality or creed would be utterly changed just by having omniscience thrust upon them. (I'm assuming belief in causality from here on) They would know every event and every cause and effect from each and every action. The person would be infinity empathetic to every other living organism and would be in complete understanding of all physical and metaphysical phenomenon. If someone did know that, wouldn't you trust them to do the right thing? A single individual's suffering would be their own; now multiply that by the number of organisms in the given universe and that's a pretty heavy incentive to play nice.
In fact, would they really have any freedom to act as they chose? Wouldn't they know what they would do as soon as obtained omniscience? If nothing else, they could create an alternate universe and create another sandbox with which to exercise his or her will. (This is also assuming that, at the bestowal of their godhood, they weren't the original deity who created the universe in the first place, but this gets into perceptions of time that would really extend this question.)
Sorry for rambling, but, again, interesting question.