I agree with Stephen, Janet and Joanne! I had to chuckle to myself, because your question asks about teaching older adults “light” cardio and resistance. So, I think that Elvis, or Little Richard just might get them a bit too revved up (only joking)!
Definitely canvass your group (I do it via a written poll or suggestion questionnaire where you limit their choices to music that you currently have or have access to so that you’re not having to chase all over looking for specific sound tracks etc).
Good luck and have fun with your new class/group!