that's the beauty of IR - projected light isn't usually in the IR spectrum, so there won't be any feedback.
to have full control over the image, you might want to tape over the IR transmitter on the camera and use a more focusable IR source, like a couple of profiles with enough filters in them to cut all of the visible frequencies. i tend to use a dark blue, a dark red and a dark green, and have my lanterns at around 40%, focussed on the dancers but off the floor. its worth trying it with the in-camera transmitter first though.
LED lanterns are also invisible to IR, so if you need to change the light the space whilst tracking, its best to use these because they won't have an effect on what Eyes sees.