Let's start from a shared agreement that the Chicken Dance, Hokey Pokey and YMCA are not for everyone. Most clients agree that they don't want "cheesy" music played at their event. I have always interpreted this to mean that the music and the presentation of the music should not seem forced or cliched. You want your event to be reflective of you and your guests. Where it becomes challenging for a DJ is coming to a clear and consistent expectation of where to draw the line in the Velveeta. One person's "We Are Family" is another person's "Margaritaville."
DJs should work with you to get a solid understanding of which songs are OK, which songs are maybes if requested and which are grounds for dismissal. You will be well served by giving your DJ Today, DJs can and should be able to draw from the world's catalog of music. The cloud provides us with ready access to nearly every song ever recorded.