Bernie, as to what to play for the 30-40 year old's, Gary gave some good advice. But let me add this: Just be yourself. Give them your best stuff, whatever that is. Even if that's " old time grandpa music" like Sinatra, Elvis, Glen Miller, Hank Williams, Beatles, Stones or whatever. Most people can appreciate a good artist that is authentic, even they play "oldies". Do what you do best, and if you're still concerned about catering to them you can play the music of their era ( 90's -2000's) in "DJ" mode on your break.