Never ever ever ever give money to someone that promise to give it after to charity. There are countless stories with proof of people who never kept the promises. Even if they did give it, they get tax benefit instead of you. It's worth also (even more) for shop or other places that propose to round up the total and give to charity.
You want to give to charity? Just give to charity, why a middle man ?
If there is one thing I can proudly brag about is that I'm part of the Elite that have that running for several years. With few hiccups of missing sessions, and sometimes extra games on the same week as the "main" game.
For those stuck looking for groups, just start it yourself, you'll be surprised how many people around would like to try and will probably like, but don't want to start the thing themselves.