The potential for moral confusion in a liberal-minded family--unpacked so ruthlessly in Noah Baumbach's The Squid and the Whale--is scrutinized with more ambiguity in this good-natured comic subversion of the holiday get-together. Diane Keaton, in a performance full of unexpected accents and grace notes, presides over a large New England tribe; their open-mindedness is tested when the oldest son (Dermot Mulroney) brings home an uptight girlfriend (Sarah Jessica Parker) for Christmas. All sorts of comic twists ensue, giving most of the characters a good workout. Thomas Bezucha (Big Eden) wrote and directed; with Claire Danes, Luke Wilson, Rachel McAdams, and Craig T. Nelson. PG-13, 102 min. Century 12 and CineArts 6, Chatham 14, City North 14, Crown Village 18, Esquire, Ford City, Gardens 1-6, Golf Glen, Lake, Norridge, Village, Village North.