Actually it may take more than 3 months for MR points to post. They do it once a quarter, but I don't know the lag time after the quarter is done. I haven't received any points yet, but I'm in no rush because I am enjoying the volunteer project I'm on. The points will be a bonus.
I don't know anything about how to get a charity registered with this offer. You will have to look through the websites noted in Mia's post above.