Don't worry...
First, on the cruise, your room is always within walking distance, so you can take him back there at any time without any major complications.
Second, he may surprise you. Try to keep a couple of his favorite things with you. Ie, a blanket, stuffed animal, pasifier, or snack. And remember, it's not just your son, and most likely the people around you will have had been there at some point in their lives, too.
If he does resort to the screaming fit, go on with your business without paying it too much attention to it. He may get tired of it and find something more stimulating to look at or do in his new surroundings. The more you cater to his crankiness, the longer it most likely will last.
Good Luck and relax. After all, you'll be on vacation!!!!
