Continuing with the cruise thinking... There must be some point where the shuttles from the port to the ship end, and the ship departs for its destination. So, would there be a cutoff for boarding like there is on real cruise ships? I would think so. That would make this very different from a hotel where there is no hard stop for check-in.
I would expect that once the final shuttle arrives with the last passengers, the first big group activity would be some type of departure party (after the muster drill), like a cruise ship. Prior to that, passengers would be settling in, unpacking, getting some food or beverage. That might also be the time for the guests to get "into character", getting their costumes, etc. The departure would be the start of more organized activities.
For the one full day, a visit to Batuu, of course. There would probably be other activities from which to choose, similar to excursions. I wonder if guests will need to sign up for excursions prior to boarding, or if that is part of the arrival day activities...
Now, checkout day would likely start earlier than 11am. For the overall effect, passengers would need to disembark via shuttles back to the port. Perhaps they would need to request a departure time, or be assigned a departure time. On that day they would also need to return the costumes. I would expect an early breakfast, then staggered departures via shuttle. It would be really cruise-like if guests had to put their suitcases outside the rooms the night before and then pick up the luggage at the port.