Yes, I agree, check your ADR. They do tend to "add" lunch during Spring Break but check to see if it is B'fast food or Lunch food. In the past because of so many people, they have added a meal and it is a duplicate of dinner.
Interesting, I briefly saw at 11:50am ressie for 2 for Saturday, April 10th. Looks like lunch might be on at Chef Mickey's!
I went to lunch at CM during the special lunch offerings during free dining 2008 and the lunch menu was very similar to what you'll find for the typical dinner menu offerings - roast chicken, mashed potatoes, Mickey ravioli, carved meats, etc.
We did lunch there last September during free dining. The menu is basically the same but there's no prime rib and a cold cut, sandwich bar which I do not think is at dinner... at least that's what it was when we were there.