Nothing shouts Christmas like a visit by the Leahy family. Their fiddles and fancy footwork propel everyone within range to their feet. Once again, they bring their Canadian musical heritage of Celtic melodies and dance to George Mason University’s Center for the Arts. Two years after their last performance there, the eight siblings from the family of 11 musicians reprise an evening reminiscent of those they enjoyed as children. The band members are Angus, Donnell, Doug, Erin, Frank, Maria, Siobheann and Denise, who is filling in as keyboardist, dancer and singer for Agnes, currently awaiting her next baby. To double the joy, the band is joined onstage by eight precocious nieces and nephews for an outpouring of musical traditions.