I'm afraid I don't have an direct suggestions concerning this, but would suggest you to contact charities that already have fully operational websites. Hopefully they will be able to make suitable recommendations & offer related advice.
I think the Registrant or Admin linked to the respective site is the appropriate person to contact (somebody correct me if wrong).
Here's an example:
Charity: Tearfund / Website: click here
A search for tearfund.org at click here, will give you this info click here
So you would make contact via the Registrant or Admin email addresses mentioned there.
And likewise with any other charity that has a website.
Incidentally, Sir Cliff Richard is Tearfund's current Vice President. G
P.S. If my post proves no good, try posting your queries in the PCA Webdesign forum click here