Explorer’s club for 3 year old

Hi all! We’re taking an 11 night Alaskan cruise in May with my 3 year old son. He’s potty trained (though has an occasional accident) and loves organized activities but gets nervous about free play in new environments with new people. He has lots of friends at pre-school but he’s known these kids since he was an infant and he’s skeptical of making new friends.

My biggest concern is that he’ll hate it day 1 and won’t want to go back, but we really want some time to explore the adult activities on the ship too, so I’d really like him to participate in the kid activities.

Any suggestions of how to help him acclimate to the kid’s club at the beginning?

Thanks!