We were in Jamacia in December with our then 15 month old. They did not actually have whole milk at the resort and he was drinking 2%. I would contact the hotel and make arrangements to bring your own if they can not.
Air travel was difficult as I could not rationalize with him at that stage. We did have a cancelled flight which complicated things. I would encourage bringing lots of things he has never seen before (stickers, books, treats, crayons, etc.) My son is very good natured but for some reason did awful on the flight. He was that kid (kicking the seats, screaming blood curling, throwing books over the seat, etc). My husband and I disagreed on how to handle it which I think may have escalated things. I wanted to just give in to him whatever it took to make him stop and my husband felt that we should expect the same manners on the flight then at home. Perhaps having an agreed plan will make it easier before hand.
Our son had a great time and loved the beach. It was just the flights that were difficult, but so worth it. Have a blast!