BUT, some people arnt as trusting as i am and some people WHO are of age dont use credit cards or any plastic. so what do we do there?
Well, there's always the option of not letting them use the Casino section. Remember, the place will be nearly inconsequential, so it is completely up to them whether they want to do what it takes to gain access.
This goes for any method a designer may choose for verification, not just credit cards.
Of course, there may be less objectable methods for verification that greatly smallificates the group of potential skeptics. But there will always be a group that does not want to do that which you may ask of them. It is just a question of how big of a group is too big.