Angel Flight and Part 91

This is a 2-parter:

(1) I know there is a waiver or Chief Counsel's opinion or something that allows
pilots without a commercial pilot rating, flying under Part 91, to carry Angel
Flight passengers in a way that would otherwise be prohibited. I know I've seen
such a document on the web somewhere, but I can't seem to find it. Can anyone
come up with a pointer?

(2) If memory serves, the above document restricts the waiver to something like
"carrying passengers for the purpose of receiving medical treatment". I am
seeing lots of requests for pilots to volunteer to transport kids to a summer
camp where they can have fun with kids with similar disabilities. Is it legal
for me to fly these missions? Would you accept such a mission?

Dave