I am happy that you donate, I think more people should. But to your comments that Gencon should do more, I think your comments are misdirected. Gencon puts on events to help generate the money. Its a fine line that needs to traveled between promoting the charity events and getting all up into attendees faces. We've all had that overly aggressive group requesting money and it does more harm that good.
Could Gencon do more to promote the charity events, maybe. Could attendees do more to support charities, probably. In the end these are personal choices. Some prefer to donate their money to their local charity or one they have a personal connection to while others give to as many as they can.
And I do want to correct one thing on your math. Unique attendance (number of badges sold) was about 60k, so that works out to about .83 cents per attendee this year.
In the end, I'm happy that Gencon does charity events. They give people the option and that is more than other companies that run convention do.
I applaud your support of local charities as well as those who read this and support theirs.
And for those who do not support a local charity, why not? There are so many (cancer research, homeless, food pantry, animal shelter, etc) to choose from, and they will all be happy with anything you can spare.