This seems like a good idea, but I think you need to rework your percentages.  Maybe if you could make this more enticing than the other charity lotteries, and no offence, but what makes this better than Bitlotto jr. (aside from the charity thing)?  If anything it's worse, my advice is to make charity optional, the max a person can recieve from the lotto should be about 95%+, and the tickets should have one flat price like .01 or .05.  Yes your intentions are good (I hope), but what you need to consider is that most people aren't that generous, even if they got the whole pot some wouldn't bother to take the time.  So, for some it's not about generosity its about their time, and if they think it's a waste they won't do it.