Read this!
MSBJPlayer is right, MO enforces the law against the underage use of fake ID.
Here is an question to a lawyer from a father whose son entered a casino with fake ID, and the lawyer's reply:
http://www.justanswer.com/criminal-law/6auzc-son-just-citition-using-fake-id-enter.html
And according to another article, the owner of the fake ID isn't the only one to be penalized: not only will the person using the ID be arrested and prosecuted, the casino operators will face hefty fines. That's the last thing they want or need, so they'll be on the lookout for you.
http://www.semissourian.com/story/1894534.html
Bottom line: you are breaking the law, and if you get caught, you'll be in deep shit. Just because you live in MO doesn't mean you won't be punished if you get nailed. You could face fines and imprisonment as a result of your actions, so (quoting "Dirty Harry"), do you feel lucky?
Think about it.