need advice on setting up for portrait shots in senior center

I would not start using flash on a project if you haven't used it previously. Practice on your friends.

I really recommend window light.

I'd start using natural light for this project, too. Even window light requires some practice, so maybe you want to start by simply placing your subjects in open shade. Then, add a simple reflector (gold/silver/white) to bounce some direct sunlight back onto your subject.

If you'd like to use flash in the future, a good place to learn more about (small strobe) flash photography is the Strobist website at
http://strobist.blogspot.com/

Cheers,
Andreas