I think a clean credit card with a great credit level is a must but even more important is that you check the expiration date on your credit card. This is obvious right and so is taking an extra set of passport pictures which every good traveler knows will save them a lot of time and money if their passport is lost. The cash question is interesting if you figure $100 a day that amounts to about $700. Now I know everyone knows they should have some legal tender - how much I reommend is about half of the amount in cash and the balance should be in travelers checks. Travelers checks would be my main financial instrument because what I don't spend I can exchange for cash when cruise is over. Also ships are generally pretty good about cashing travelers checks. I don't know if they give cash advances on credit cards without putting on some kind of service charge.
Maybe someone knows.