Can you not take it with you? That's what I plan to do. We're paying a little extra for a room with a mini-fridge and microwave (not sure if that's available on a cruise). So I'm bringing applesauce and BIO-K, and maybe some oatmeal packs. There'll be plenty of food there, but it's nice to have a safe backup in my room for inbetween meals or early morning/late night.
I think cruises are good for food in terms of getting specialized things. My friend who is diabetic went on one and said the cooks were fabulous, and food was available pretty much all the time.