We are late night eaters too. One too many times the kitchens have been closed on us around 11.
When are you going? What day are you arriving? You will have better luck with the kitchens staying open late on a Friday or Saturday night. If you are going during a slow period though, it's up in the air. They never have a set time to stop serving food. Arriving on a Tuesday in early May? Good luck. Arriving a Friday night during Spring Break? You should be fine.
Rule of thumb is to ask as soon as you arrive what time the kitchen is closing. Then order about a half hour prior to that. Trust me on that. There have been days where hubby has eaten peanut butter that we got on our grocery stop for "dinner" because everything was closed, and he didn't feel like room service.
As I said in another thread, there is a walk-up counter service pizza place outside, in between Margaritaville and Pat O'Briens. They tend to be open later, but again, no set time on when they close.
My advice to you is to check in ASAP, leave your bags with the bell hop to be delivered later, and hoof it to City Walk if you want options.