If you are asking to find out what kind of cakes others have gotten, you can see that on the cake thread. I know it's long, but there are some pictures and descriptions on that thread, it's why there is a cake thread.
The only way for you to know for sure if you can get what you want is to call the cake hotline and ask for a dessert suitable for a diabetic, with decoration to commemorate a cancer survivor, to be delivered to a WDW restaurant. Let them know which restaurants you are attending that you might have the dessert delivered to. Then find out what they can tell you about where would be the best place to order something like that. If you have a price in mind, communicate that to them before you order anything.
The restaurants themselves won't do this kind of custom cake or dessert for you. They might be able to write something on the plate though, that sort of thing.