I agree with Spectral1212. Helping and charity are fine as long as they don't run the helper down. If you become drained you'll eventually lose the attention you can afford the man, perhaps your patience. If it ultimately affects your health (as so often it does when someone becomes stressed) you'll be looking for ways out. So probably best to make your views plain now. It may not be easy but take courage. You can't be expected to hold down a full-time job then give up the weekends, plus the worry of what's happening when you're at work.

Calling the Association is a good idea. They may be able to advise about "professional" assistance.

Best wishes with it.