Take cash with you. The ship ATM's are set at $5-$8 to get cash. Bring a lot of singles and just keep in your safe. I used my credit card for all large items such as bar tabs, lunches and excursions but used $1 bills for snacks, some drinks, tips, some shopping etc..
I had $400 in cash for 6 people for 7 days and brought $100 home