What's the age diversity? Race diversity? These are all relevant questions. Assuming white with a large range of ages, try to play music that generally everyone will appreciate.
-Patsy Cline
-Perry Como
-Frank Sinatra
-Neil Young
-Miles Davis
-Johnny Cash
-Three Dog Night
-The Hollies
-Elvis
-David Bowie
-CCR
-Beatles
-Bob Dylan
-Smashing Pumpkins (the easy shit)
-Red Hot Chili Peppers
It's hard to find music that everyone will like but still keep things up-tempo. There are songs that sound better while you're drunk, keep this in mind and put them towarRAB the end of the playlist. It will also be easier to be more experimental with what you put on while people are loaded, assuming there will be alcohol.
Cheers.