in no way is there room for a pack and play in the restroom. Our DD (age 5) is a very light sleeper as well and has never had problems on the ship. Are you in an interior or OV cabin? OV have a little more room IMO and you could place the P&P front of the bed. The only light comes from a crack under the door or the moon in the window which can be blacked out with the curtains. I would not worry about it frankly, you will be surprised how well she sleeps because of the rocking of the ship! Also, you could bring a sound conditioner (white noise machine) to block out noise. As far as leaving her, that is always an option but she could go to Camp Carnival and have a blast and you and DH could have some alone time.