Barb, hope your fatigue is gone, or at least better. I had to watch myself today and I almost bit off more than I can chew. I started on outside projects, got tired after a while, and finally told my dog I was tired, was going in the house, and couldn't stick around to throw things for him to fetch any longer-- after entertaining him with his "fetch" toys for a little while (BTW, we have great 'conversations,' LOL!).
Tomorrow I intend to do more mellow projects inside the house!
Never feel useless--and so sorry you're feeling that way. But I surely know what you mean when you say you never know when a flare will 'hit' and you won't be able to do what you volunteered for. Oh wow--been there, done that, and more times than I like to remember!!
I found if I wanted to do something for my church or school, I had to ask what they wanted help with---something that I could do from home.
I'm sure they can think of all sorts of things: prayer chain phoning, organizing upcoming events on paper, make things for the school (cutting out, gluing, etc.), keeping track of things they collect like Labels for Education points (sometimes involves some cutting or trimming), being in charge of a collection for the poor or other charitable organizations, helping with church bulletin prep, anything that you could do on the computer, etc..
I help out at church/school from home when I can, and once had to turn down another project they offered me that would have involved lots (more) phone/contact work (I already make several phone calls a week and also some computer contacts). I move slowly, and can just do so much.
Anyway, I would guess they could come up with a few ideas for you. Best wishes and take care!