For several years we had a wonderful lady dance with us who was totally blind (could not even tell light or dark)- here are a few things I learned from her

She always danced in a line next to a wall - the reflections off the wall gave her as good a sense of direction as the rest of us.

Use dances where you stay connected to other dancers.  With her experience she did well on dosido and hey - but down the outside alone was not possible.

You will have a problem any time dancers need to make new connections - like ladies chain, allemand, etc - someone has to be able to find the impaired dancer's hand.

She would not dance squares - too much uncertainty and dancers who are lost made it impossible for her to recover(in a contra you get past it quickly so only one time thru is challenging).

As I said - this dancer was totally blind (but so good that those who did not know her often did not figure it out).  She also clapped at times when not connected to hear what was around her.

It sounds like your dancers will have various degrees of impairment, so some of this may not be as important. 

Hope this helps some - while challenging - this should be very rewarding and fun.

Mac McKeever

St Louis