I would keep everything in Bitcoins when running the site.

Remember, Bitcoins isn't real money, it's not even backed by any government!

By keeping everything in Bitcoins, there is technically no money for them to seize. Let the players figure out how to convert it.

You can store them in such a way where if you do get busted you can still have a third party honor all of your players withdrawals.

The only way you will get busted is if you get pretty big and actually start making out pretty good, once that becomes the case you will also be in a better position to defend yourself, especially if your resources can’t be illegally confiscated.

Not only that, but the US government is basically going to have to make the argument that gambling with fake money is somehow illegal, and if that's the case, well, they better go after all of those online MMORPG's that have ways players can gamble fake money.

“The question isn't who is going to let me, it's who is going to stop me."
-Ayn Rand.