@Mightydan Thought I'd update you on the situation. XD Turns out what I predicted was right:
http://i1382.photobucket.com/albums/ah248/Tripliss/mush1_zpsoalztab0.png
http://i1382.photobucket.com/albums/ah248/Tripliss/mush2_zpsd1y4xwn3.png
Then I used cheats to make it even smaller. This lady was determined:
http://i1382.photobucket.com/albums/ah248/Tripliss/crazyfan1_zpsaardx0fs.png
So that method apparently isn't going to work. What's odd is if I let the sims choose whether to dance and they get pulled in by (presumably) the DJ Hyped Up interaction, then they'll dance from below and use the thought bubble that shows they're dancing to the DJ and not just randomly on the floor. But if I ask them to do it as a group, or individually, with the DJ booth as tiny as possible, they just do the Red X bubble... can't reach him.
Welp, back to the drawing board.