We have alot of peeps that are basically into money laundering as you've said but, nobody really gives a f*** about where these guys get their money From; to some point, it's not even seen as something very important to follow up on serious investigations before they could let them place their bets....
AFAIK, they could just get an alliance with a certain casino, just to ensure thier safety during this illegal monetary services, So I'd say No. Casinos could sometimes be an avenue to launder 'em cash.

Sandra 💇