You might want to figure out some way of compensating the participants with some portion of revenues received (if any) from the broadcast/publication of your documentary or whatever you want to call it. If you make a film of me, and others pay you to watch the film, I should get some percentage of the proceeds. Even if it's not a huge percentage (obviously you have your own production costs and overhead you'd like to recoup), taking the time to do that and adding that into the contract with the participants would make things feel a lot less scammy. As it stands now, it appears you could get lucky and make some significant money from your film(s) and not be obligated to pay the participants anything, which seems unfair to me. Or did I miss some fine print somewhere?