"The Gap Band nearly cleared the dance floor."
That's a travesty.
Here's the ultimate piece of advice: Keep it upbeat the entire time. Don't think, "Oh, I think we'll want to have a slow dance in there for the couples."
No! Get that thought right out of your head, Mr. Mix in some more obscure stuff if you want, but keep it all upbeat, four hours if you have to. This isn't a time for you to show off your rare Talking Heads seven inch collection. Play to the crowd and have fun.
Congrats, btw.