It shouldn't matter what you eat when you go and I don't think you even need to tell them when you book. I was unable to get CR for the day I wanted. I just booked the rest of my ADRs last night and CR was completely booked, for dinner, the day I wanted but you may have better luck at lunch, or a little later. That's what I did for SciFi-going at 1:50 for late lunch or early snack.