I just booked on the Wonder for three days. It'll be our very first cruise. I understand that most of the cruise items can be charged to your stateroom and settled with a CC. I think we'll also put the end-of-cruise tipping on the CC. However, with my wife, myself, and three teen girls, how much actual cash should I bring onboard and for what? In other words, what MUST, or should, be paid with cash. Thanks!