You're doing good works; it's fine if you do them in a few new places to meet a few new faces. But like anything, if you work hard at it, you will succeed.
Not everyone will be single, of course, but usually, many singles also attend specially announced events.
If you don't meet anyone on the first couple times you volunteer, pick a new outlet for your energies and see that one works better.
I don't understand why more mature men do not take advantage of spas; they're fabulous opportunities for singles.
When you hang out informally with women and get to know them in classes and over group dinners, you have a great chance to become friendly without too much pressure.
You already know that bars are a bad place if you want to find someone who is serious about finding a life partner (anyway, they're usually full of twenty-somethings who'd consider you an antique).