My suggestion of launching the attack on Christmas Eve seems (at least at first glance) to be a wise decision. Not only are the Death Eaters present all more or less drunk, it's also a surprisingly small group. Granger's Homenum Revelio, which she casts after we've blasted the mansion's huge front door with a well-aimed Bombarda, lets us know we're dealing with no more than twelve people. And that's only half of our own manpower. A positive development.