Content goes a huge way in getting the user to engage the site. BUT!
I think of online giving in the same way as selling a product. Churches needs a clear and outlined click path to get users to the donation areas. When I am planning a site layout and the church want to see more users utilize their online giving option, I create a clear plan on how a user would get to the donation area. We make sure that call to action buttons are placed in a locations that are relevant and easy to find.
Today I found this article: Donation Usability: Increasing Online Giving to Non-Profits and Charities, by Jakob Nielsen, which is summarized with:
You might find it interesting reading. What have you found to work when it comes to online donations?