As long as you don't bet with chips that are used in the casino to represent money anything goes. Like they use for poker tournaments and such. Those chips have no cash value and you can basically do anything you want and most likely if you have that many people the casino will provide tables and dealers for a variety of casino style games. You can make up your own rules, whatever you want.
At the end of the night, whomever has the most chips or the chip with the x on the back or whatever wins prizes and such, that is all fine.
They don't have to follow gambling laws if they are not betting money - it is basically games for fun