The funny thing about "I Could Have Danced All Night" is that every opera star (Birgit Nillson, Angela Gheorghiu, Maira Callas, even Tebaldi) when wanting to sing an "American Song" in their recitals, they would choose that one. I never understood why. Is it because it's more operatic than say, everything else? Anyway, just though it was funny.
Maybe try looking at something from the early Operetta's, like Babes in Toyland or Showboat!Think of Jeanette MacDonald. Hope that helps a bit! Good luck!
~And let us try, before we die, to make some sense of life~