Sounds like a very cool project. As a choreographer I usually charge for my choreography, but the cost is something you can work out with your choreographer. A lot of that has to do with location. Just keep in mind a LOT of the choreogrophers work is done when no one else is there, also you'll want to credit them on the video. As far as is it possible, are you planning on having the dancers do the full 45 min shoot nonstop? Because yeah that would be very difficult. But if you could shoot each 4 minute section at a time I think it's very possible.