I wonder if anyone has considered assigning some more hindered dancers a role that is not dancing? Could even make up roles for them. They could help make sure sound is ok. Could help refill water. Could make sure people's stuff isn't left. Other roles? Helping to set up. It wouldn't have to be a real job, just something where they could feel welcomed and useful. I think it's sad for someone to hear they are not welcome, and if they could be 'reassigned,' something like "We feel you may create hazardous circumstances on the dance floor both for you and for others, and in addition we really need________ role filled. Could we recruit you?"
I did this in the after-school orchestra I used to lead, and though the scenario is different it may still prove somewhat relevant. The orchestra's goal was to get kids off the street, so turning them away could mean that they ended up somewhere much less safe than with a violin. There were some kids who just didn't fit in the box. One I recall was significantly younger, and one was particularly advanced. One was really hyper-active and sitting for an entire 1.5 hours was not a posability. I used their abilities differently than I did the other kids, and they not only took their roles very seriously, but added to the quality of the experience for the other kids. It also provided a way for the other kids to see how being out of the box could actually help them out.
That gives them an out and does not ostracize.
Just a thought maybe someone could use.