I have seem many good jazz bands play miserable ballroom programs. Once it was so bad that the good dancers waited for the canned music during the breaks to take to the floor! Or the conductor that announced, "I don't know if you can dance to this but here it goes..."

IMHO, please, please, please...

Keep the tempo constant. Dancers don't like "creative" tempo changes.

Play with exact, correct tempos, although some dances tolerate range of tempo more than others. Waltz standard is 87 bpm. Foxtrot cannot be danced SLOW -- don't think you are doing older dancers favors by slowing down their Foxtrots. Realize that in EC swing, the "real" swing, triple-step, needs slower tempos that single-step. Pepping up your swings to fast tempos will frustrate the triple-steppers. Rumba has a range of tempos, but works best in the 100-110 bmp range. And so forth.

Be a but careful, though. Full, standard-speed Quickstep's and Viennese Waltz's demand good dancers to keep the floor safe! These you can slow a bit.