You bet they accept yankee dollars--- all they can get !!
The Atlantis is something to see, especially the Dig. I'm not much of a beach person so cannot comment much on the beaches, snorkeling, etc.
Don't know your likes, dislikes, etc. but a tour of the Atlantis and then back to the dock area for some shopping at the famous ( or infamous ) strawmarket will pretty much fill the day.
Maybe someone else can offer some help on other excursions.
whatever you do, enjoy and have a good cruise. :wave