One should only wear a white tuxedo if you are in the tropics otherwise you run the risk of being mistaken for a waiter....!!
People generally know how to dress on Celebrity cruises so the black tux should suffice.
What were the other Cruise Lines/Ships on your last? I would expect white /black Tux's to be prominent on Celebrity. On the Galaxy last August I witnessed 2 occasions of Gents without jackets refused entry in to the main DR on formal nights.
We are on the Constellation on 7th Feb, this will be our second time on this ship at this time of year in the caribbean. please get hubby to take his tux, he will feel left out with out it black or white it does not matter, have agreat holiday and enjoy yourselve.
I always take the white tux whether Med or Caribbean and just back from a cruise in OZ and NZ. On the formal nights the waiters were white whears normally black, so I wouldn't worry. I would confirm more and more are going black and many just with a smart suit. On the last trip out of around 350 males only about 50 had a white tux.