No, it's safe to say, improvisation on a lackidaisical piece, is always appreciated by an audience. Loosen up, relax, have fun, and be in control. Good voice, singing is my passion, piano comes as a side note. And to block critics, just write your own arrangement, and say arranged by ___. Keep it up. Get a voice cooach if you dont already have one, becuase singers, whom play piano, are paid more. At least in small gigs.