You have gotten mostly excellent advice by being smart enough to check in here!
I can only add that taking along a few singles and/or fives in cash allows you the opportunity to choose to offer a tip if you want. You have already paid the cost of the excursion and anything else you want to buy can be easily purchased with a credit card. I guess I'm trying to offer advice; do not carry a large wad of cash with you. It is just common sense.
And enjoy your cruise and your excursions!