This is not a bad idea... WHat are your methods you are using to create the scratch-offs and preventing light viewing?
I haven't researched light viewing so much yet. I'm still not sure it is legal to sell games like this even for charity in the US. I'm sure that the scratch off material itself is very light proof. The cards I'm making are just a mock-up for fun. This project requires production methods not available from traditional scratch-off printing services. I'll need a customized design and strict protocols will need to be followed. This can be done on a small scale easily enough, but it's very labor intensive. I know what I want to make it work and scalable, but have limited resources at the moment for development. I'm not in a big hurry, because the Bitcoin tools are still too immature.
What I hope to do is get local business to sell these games on behalf of charities. Winners would be able to redeem them anywhere, even at home. People can have parties playing these games and shop online with their winnings. My only real issue is its legality. It's a little too much like lottery games even though in many US states Bingo is legal for charity purposes.