We went when our son was not much older than that, he refuses to sleep in anything but a crib at home-but there-he wanted nothing to do with a pack n play (although honestly he was getting a bit big). The state room host was glad to take the pack n play back and get us the side rail. I laid with him on the fold out bed with a side rail-and most nights was able to sneak back into my bed when he fell asleep. Honestly, they will probably crash so hard, as long as they are in a safe sleeping environment, they will be just fine and probably sleep. Would they be willing to sleep together in the fold out bed with side rail? That would make the most space sense. That being said-you can plan for them all day long, but it's going to be whatever works at that time

Good luck!