Kingsley had literally growled at Draco's tone, but had agreed, in the end, to his terms, even swearing to it magically with an exceptionally sour expression on his face as Hermione performed the spell. They determined that Draco would do his best to bring Voldemort, Bellatrix, and Harry all to the same location while Hermione kept watch though the mirror long enough to figure out where that was, relay the information to the Aurors, then Apparate there to help Draco and Harry hold them off long enough for the Aurors to make their way through the Manor to them. 