Don't do either, then. If you don't want to give money, just give a polite and firm "no". I can't believe that anybody takes such a response personally.
To be honest, it's no wonder this guy is harassed by the homeless if he is handing out $100 to them inside a week.
As I read the article, I didn't really interpret it as he was actually giving out $100 a week, but rather saying that if you gave a dollar to everyone that asked, you could spend a lot of money.
We're also talking a specific week here, not at any given moment. I've never been to WWDC or SF during a big conference but if I was a homeless person looking for a place with a lot of people who is sure to have money, I'd look at the WWDC crowd.
If you have any genuine sympathy that will probably come across to them.