In my opinion and experience, I'd say do it because you like the charity or the people involved. If you do charity work for other reasons, like marketing, the Karma bug bites you back.
Early on in my business ventures I would do these style of events thinking I would get great publicity and the phone would just start ringing. In the end, while everyone was super stoked to have won the "no-stops" detail, they never turned into repeat clients and none of the leads generated at the event never turned into what I had expected. I felt disillusioned.
But do it for the right reasons and you'll get more out of it....business wise and personally. Just my thoughts.
