You would need cash which can be arranged onboar.
Our experience was that you could get gaming machine tokens charged to your cabin but there is a (5%, I think) surchage.
My advice would be to have some dollar bills with you. (They're cheap these days). Enjoy the cruise and good luck with the machines
You do ned Dollars but the best way is to go to the casino/and cahrage them to you credit card that way you avoid the rip off charges at reception/pursers office
good luck Horswil.