Do you think things would of been different if Ryan and Allison knew what was going to happen?

It really all depends there is a possibility. I think they probably would have because it would have been on their conscious and practically eat them alive. Also they know its wrong and that is a probable reason of why Gary and Brendan committed suicide (Plus they wanted to take as many people as they could before they died.) If Ryan and Allison had known about what was going to happen they would have stopped it, or at least try to knock some common sense into them. In the text when all of them were together in Blast Zone, I think Ryan and Allison didn't think it was much to worry about because Brendan and Gary picked up everything and were interested in it they probably thought it was a science experiment. And if they had known they probably would have thought that Gary and Brendan were joking, and if they did believe them they would have thought they were crazy and have told the authorities.