I wouldn't worry myself over this. If I really want to make a donation, I do. If I don't, then who's to know. I think a well-penned letter of condolence sometimes shows more concern than just sending someone a check or making a donation.

As to donations and charities: I blot out my name on the check, scrawl my sig, and use no return address on my envelope. Keeps those compiling sucker lists at bay.