May I use video of retirement home residents if I was promised release forms pre-shoot, but then denied release of a few residents post-shoot?

I was contracted to do a promotional video for a non-profit organization that builds wooden toy cars and ships them to less fortunate children around the globe. About 2/3 of the video features the volunteers who build the cars, but the last part features a local retirement community that the charity partnered with. A small group of residents at the retirement home take a few hours every month to voluntarily put the axles and wheels on to the cars. The charity wanted a blurb about this activity in their video, which they paid me $500 to make. When I got to the senior center and was halfway through filming, one of the employees told me I wasn''t allowed to shoot the residents faces anymore. I was able to obtain releases for some but not all of the residents. The non-profit is my client, not the senior home. I have written consent from them in an email prior to the shoot. They also want to use the video as a promo tool. If I show faces, can they sue me?