I know that during the Millennium, the ship anchored off Rio for the fireworks. Unfortunately, I don't know the activities. But I'm sure you can set up some of your own by searching out Carnival parties on the internet. I lived in Rio and most cariocas (citizens) leave the city for other areas becuase it's a wild place.
The samba parade is tough to get into. But Crystal may buy tickets in advance.
Suggest you call them -- if they do have tickets for the big Parade, you're in great luck!