If you'd like to donate to the ACLU in a way that lets you easily change/cancel your donations, I recommend using Sublime Fund (https://sublimefund.org/). Disclaimer that I am a founder. We deduct the cost of credit card processing, but we don't charge any sort of platform fee.
Donating should be easy, but canceling should be just as easy. You can do it through our website anytime without speaking to anyone.