16-35mm is good enough for most of time for inside ship photography. I took this ship on last Christmas to Bahamas and I used mostly 16-35mm + SB910 (with diffusion) for inside scenes and 58mm for portrait if I wanted a nice bokeh. Even the light inside is not that dim, I always used flash if possible to avoid shaking and high ISO.
Actually most of my photos were taken outside and on shore excursions using:
Nikon 1 AW1 for video of underwater/snorkeling/water sliding, etc
GoPro 4 Black for sports like parasailing
Nikon V3 + 70-300CX for wildlife (alligator at Florida).
Most important is enjoying your trip! I usually depart from NYC and NJ but last Christmas I choosed MD since this is the only ship stops at Key West FL. The boarding/debark processes and US Custom are much faster and smoother at Baltimore.

From Grandeur Of The Seas: Quantum of the Sea on left side, Disney on right.

Quantum of the Sea, Grandeur Of The Seas and Disney