volunteer work, safety checks

Having researched online about various volunteer agencies operating in Africa, I have decided instead to travel alone without joining up with one. I am a little older than your average gap year volunteer and Im not keen on paying through the roof to an agency without the bulk money going to the local community. I came across a website offering hostel accomodation and transport from airport etc and when you get there you can choose from a variety of projects in the area to work with, depending on your time and expertise. Rather than being an agency it is just a service run by an Irish woman to help individuals like myself who want to volunteer but for whom going it completely alone is too daunting.
It all seems great, however I ought to do some checks before I head off into Africa (I am a young woman travelling alone) to make sure its all ligit.
Does anyone know exactly how I can make these checks?

Ask the lady to put you in touch with some people who have already worked with her? And get more than one reference. Of course, do the search on google as well.

Try the Lonely Planet Thorn Tree forum.