Anything by Sinatra, Don's list, plus a host of others that folks can dance to.
If you're trying to appeal to 30-year-olds, folks born in 1975, then you're going to want music that was popular in the early 1990s, music that came out when they were about 15 to 17 years old. That's a tough nut to crack. Naturally, this will depend on where you intend to perform and the atmosphere of the venue.
Check out the song list on my web site and you'll find there is a lot of diversity, and this is just a partial list. I sing nearly every song on that list, which is about 350 songs. It will give you a starting point.
Good Luck,
Gary
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Travlin' Easy
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)