Joining in! Sound like a fabulous trip!! We did a 4 night cruise on the Wonder in 2010 and a 5 night cruise on the Fantasy in 2012. Both times at Nassau and
Castaway Cay. I don't recall there being character breakfasts or Disney Jr. show two years ago, so things may have changed a bit, but if you have any specific questions, I'll be happy to give it a go.
With respect to getting off at Nassau, I really wasn't too impressed. I'm sure it would be better to do an actual shore excursion, but just walking around the port and exploring the town wasn't that big of a deal. We aren't big shoppers though. If you like to browse shops and stuff, then you might like it more than we did. All that being said, it isn't much of a hassle to get back on the cruise ship, so I'd suggest you at least go walk around for an hour or two (and maybe get your passports stamped for the fun of it.)