Most charities you can donate to anonymously, though you probably wouldn't even need to do that. I made donations that were marked as anonymous on charity navigator, but that was just to avoid giving personal info or being on mailing lists etc, and the amounts were much smaller. I don't know how secret it needs to be, but just to avoid general suspicion? I think you'll be fine even if it's not anonymous. I would only avoid political donations as those are public, but even then, I doubt anyone would be actively looking for that information and then assuming you were going to ctb. As has been mentioned, you could also set up something for after death. Out of curiosity, would you be okay sharing what your preferred charities are? I sometimes like to donate to try and hate myself less. I usually go for direct relief, water for people, action against hunger usa, along with some local things and animal charities.
