Has anyone actually seen the documentary yet?
I would find out exactly why the charity needs the footage. Is it to put it on their Web site for the purpose of helping the needy? If so, you give them some footage, let their web department do what they want.
Is it to resell to another filmmaker so that person can make a competing documentary? If so, don’t give them any footage.
Is it to make an ad to screen on tv? Then give them the footage but make sure you get a big public thank you during the spot.