With the amount of money I have spent whiles gambling and haven't won any major jackpot, I am not going to be donating anything to any charitable cause unless I have made a huge profits and to my mind most people view money from gambling as dirty so I doubt any charity will be thrilled to have them.
I do not blame the principle that you apply, it is your right. But for me when I want to contribute from the results of playing gambling, it doesn't have to win big or small. As long as you intend to do good, then do it.