not sure where you're located, but if you're in a college town that has a dance program, put up flyers there. or put them up at local dance schools. the staff or students would probably be into it. i'd just throw a link to your video stuff on your flyer; unless you can really target websites for dancers in your immediate area, it seems too random to set up the vid. on some other site.

most dancers are down for dancing, but i'd add that really good dancers are going to want to dance with other good dancers. if you have an 'all abilities' thing, it might hamper your efforts to attract better dancers.

if you want to keep it more open to all, it would help to have a dance point-person/leader, who can give some general creative direction. unless you guys are doing a purely 'free-flow' thing, it helps to have a bit of focus and parameter-setting. it actually makes it more fun and engaging. alternately, you could have different sessions according to ability.

re: the instrument set-up, personally, i prefer it off to the sides. unless the room is really huge, it's distracting to have musicians front and center. also, if someone dancing is really getting into it, they could run into you guys and someone could get hurt.

the classes i took at alvin ailey school put all the percussionists off to the side, but within view. i liked it because you got to focus more on your body, how you were moving in space, and how you were letting the music move through you.

that sounds like such a cool idea! where is this place? definitely sounds like my kinda hang!

good luck and post some vid of past sessions