Welcome Aboard, Devin!
Thanks for cruising by the Moms Panel with your question.
It's true that there are no storage lockers on
Castaway Cay for your belongings. The good news is, there's no need to bring cash, credit cards, or valuables with you when you disembark. All you'll need is your Key to the World card, which can be used to purchase souvenirs or cocktails on the island. Lunch is included in the cost of your cruise, and you won't even need to show your card to partake of the delicious BBQ buffet!
Disney Cruise Line provides guests with beach chairs and umbrellas at no cost. I've never felt uncomfortable leaving a beach bag with a few necessities (sunglasses, sunscreen, small camera, etc.) on my chair when I take a dip in the water. I cover my bag with a towel or place it under my chair if I'm away for a few minutes. We also usually try to be among the first guests to disembark on Castaway Cay day to make sure we get chairs right by the water. If we plan to rent bicycles on the island (our favorite Port Adventure), I usually try to bring a small backpack-type bag that I can wear when we ride.
I hope this helps answer your question! Please come back and visit us if you have more questions before you cruise.
Have a magical day! - Diane W.