OP - I might have another suggestion.....We just got back from a cruise with P&O. They had a fantastic night nursery where we put Charlotte for anything between 1 hour and 3 hours on 7 out of the 12 nights of the cruise - you can put them in anytime between 6pm - 2am (well last entry is 11pm).
They gave us pagers, and paged us on the two occasions where Charlotte woke up and they couldn't resettle her - it transpired she decided to get her first 2 teeth while we were away.
The night nursery was clearly a very safe/careful operation, with lists everywhere of room temperatures, how they check the babies, (who were all lined up in a total of 8 travel cots), and what they would do in the event of a ship emergency.
It was quite expensive, but I couldn't recommend it enough. The baby and children services are fantastic on board, and they supplied baby food, or the chefs would make purees out of the evening meals. They gave you travel cot, sterliser, bottle warmer, baby bath etc. We all had such an amazing holiday - the ports, entertainment, food all fantastic.
It was very clear that the night nursery was very well staffed and a safe environment. If it is of any help it was P&O Ventura which we sailed on From Southampton (so you could take as much luggage as you liked) xxx