Well, this is why you have a microphone.
...to avoid being tagged as one more slow burning wedding DJ.
It matters what the expectation is and what your entertainment capabilities are. A lot of events I do have an opening dance set - that's a full on dance floor from the moment the doors open from cocktail hour to the main room. That doesn't happen simply because you picked hit songs - it has to be lead by someone. Even if the cocktail hour is in the same room there is a key transition point where the party "begins" and again - this doesn't happen simply because you turned up the volume.