My squad looked into a raffle once - players could buy a ticket for a small fee and win a prize. Every thing we read indicated we were better of dropping the subject quickly.
Now I'm not a lawer - so we could have been mis-reading things. I would advise you to really research it out though.
For example here in michigan, we have to get a license. And from the paper work, we have to file a report detailing how many prizes were given under x-amount of dollars.
Stuff like this is highly regulated lol