Another major request I get from senior groups is " Please don't play all old music". Many of these folks are active, busy people that hear that old stuff too much from the performers that don't have a better repertoire.
Use the old standrads, but don't be afriad to include tasty, classic, upbeat songs from today too. Most 50's rock (Elvis, Chuck Berry etc) goes over great with the senior crowd. They forgot how much they hated it back then, and they can finally enjoy the energy of the beat now !

Keep it lively, and they'll swing at every pitch you throw at 'em.