Just wanted to update those who may be interested.
I packed a soft sided cooler and some ice and had my cabin steward fill it each morning with fresh ice. The milk stayed nice and cold and some was even frozen! I didn't even have to pump and dump! We did drive to the port though, so I don't know how big of a hassle it would have been to fly with nearly 5 days and nights worth of breastmilk.
I purchased some Medela brand wipes to clean my pump pieces in the absence of a sterilizer. They say the parts don't have to be rinsed after use, so you can use them in places without access to water. (think Mexico, etc.) They were very convenient.
The best news though is that my son went right back to nursing when I returned. He never missed a beat!
Next up we are taking another 3 nights Bahamas cruise on the Monarch of the Seas with both of our boys, ages 7 and 6 months. Wish us luck!