If Emmur and Will won't give in to blackmail and Cloive carries out his threat, then Emmur and Will can bask in the comfort of knowing they didn't break any promises but the whole thing will be blown wide open and, with luck, George will go to jail.
With even more luck, Emmur and Will could be charged with concealing a crime, withholding evidence, aiding and abetting a criminal or something . I'd settle for anything that wiped the holier-than-thou tone from Emmur's every utterance and got her thrown off the parish council.
One thing puzzles me: how did George have a phone number for Cloive? Surely, nobody in the family would have it and pass it on, and the last time Cloive had any contact with the Horrobins, George must have been a very small child (if he was even born then. I'm struggling with the timeline).