If you can afford to take the time off then do it. Working for a charity, I assume you don't have insurance. Funny I should say this but not having to go through a disability claim is a major relief. Remember that you are not required to tell your employer why you are taking a medical leave. They just need to know its a medical leave and the dates. Talk to your doctor. If you do have insurance then make sure you understand their terms. They decide if you are healthy or not and healthy will likely be their response.

One of the reasons I quit my job last year was due to the fights I had with the insurance company. Just make sure you follow everything to the letter.

I hope the break from work works out.
Good luck!