I need three cameras...one for each of the primes I would like to have...
As to the OP...I just went on a cruise took two cameras and two primes...used the 28mm wide angle probably 80% of the time. You can grab everything with a wide angle and they are easier to focus.
Some other advice keep your camera close at all times and whatever you do don't forget to grab your bag after it has been through the scanner when you return to the ship!
Don't let the vacation itself overwhelm you...that is what happened to me so I didn't really shoot a whole lot and what I did shoot was even more mediocre than the mediocrity that I usually produce! lol