If BiblePay takes off and donations per month rise to some serious levels, I think it's not unreasonable to imagine that one of the people in the Compassion team could actually install the BiblePay wallet and just do the exchange to their fiat account once a month, especially because they have a vice president of Information Technology. Also other executives and VPs, such as CFO or VP of finance. The devs could contact them and help them set everything up. I imagine it would then be fairly simple to explain how to withdraw dollars once a month.
So a Compassion BiblePay donation address could be coded into the algorithm for them to automatically receive payments. Then in the beginning I would not allow for masternodes to vote to change that address because of the 51% attack, but it could be allowed later when there are many more masternodes. But in the meantime, even though it's centralized, the most trusted way is definitely the actual dev of the coin sending them money. We are still early anyway.