Should I just stop being paranoid?

1. No. Paranoia your friend.
2. No. Never send credit card numbers or any confidential information over an unencrypted channel. Period.
3. No. It should be standard practice to encrypt credit card transactions. Don't encourage insecure practices.

So to sum up: No, No, No.

Please post an update once we can donate securely. Then I, and I'm sure many others, will gladly contribute :).