I would really recommend thinking it through, about what would happen IF he doesn't calm, and IF you needed to get him from the nursery. Kind of gear yourself towards that, just in case it happens. Things to do with him, etc, if he just doesn't deal well.
My cousins traveled with their then 4 year old (and autistic 9 year old) on a
Disney cruise and the 4 year old just NEVER got into the kid's club. She never even stayed there an hour. (same with the second Disney cruise, actually, but that time they brought grandma) They had thought that she would love the club, and that she wouldn't be the issue, and they never "recovered" emotionally, having planned lots of alone time for the cruise.
He'll probably be OK, but come up with some alternative plans if he doesn't.
Second to last Disney cruise I chatted with a dad who had been at dinner with his wife at Palo, when they got the word that one of their sons (brand newly adopted) wasn't enjoying the club. They had thought about it ahead of time, and the husband let his wife continue to enjoy Palo, while he went and got that one son from the club (their older child was having a fine time and didn't want to leave). He ended up getting bonus time with his new son, and *both* of their evenings weren't totally changed, in that his wife continued to enjoy the meal. (obviously if you are in a couple that loves to be attached at the hip 24/7, you would make a different choice)
They had thought about it ahead of time and had a game plan, so no one was overly "thrown" by the change.