Now here’s an unlikely karaoke trio performing Elton John hits — tennis champ and wannabe rocker John McEnroe, his son, Sean, and “Entourage” star Jeremy Piven. The three took to the mike, singing John’s “Saturday Night’s Alright for Fighting,” at Rande Gerber‘s Cafe Habana in Malibu for its Wednesday night karaoke party. A spy at the Cuban/Mexican cafe said John McEnroe also tackled Jimi Hendrix’s “Crosstown Traffic,” while Cuba Gooding Jr. did the Isley Brothers’ “Shout.”