The Family Stone, which follows an extended clan over the Christmas holiday, is all over the place in terms of tone, though I guess you could say the same of most actual family gatherings, where laughs and tears often mix. Yet the movie – for all its farce, melodrama and tragedy – never manages any emotional authenticity. It’s the crucial missing ingredient in this overstocked pot. Going to waste is the cast of Sarah Jessica Parker, Dermot Mulroney, Diane Keaton, Claire Danes and Rachel McAdams, though Luke Wilson does some nice lazy ambling in the background, as Wilsons are wont to do.