Just do what you feel comfortable setting words to.
Personally I quite like the cheesy ones like Wizzard and Slade, but just to see how you got on I'd love to see you try Aled Jones, Mariah Carey, Johnny Mathis or Bing!
I feel like I have to suggest Cliff because it's Christmas and Wham, Shakey, Band Aid might work. Depending on if we do well or not Most Wonderful Time Of The Year or Lonely This Christmas. As crowds have been good Silent Night can be binned.
Boxing Day game could be One More Sleep by Leona Lewis?
Good look anyway.