From years past 2nd-hand info...
The menu is typically reminiscent of dinner and not like a breakfast at all. I don't know the exact details and I'd hesitate to say it's the same as dinner, but more akin to the other character meal lunches I'd presume.
The characters will be there if the restaurant is open. Even if the website says only breakfast and dinner have characters (during a time they open lunch) and the phone CMs say the same (they're reading off the website basically), they will have characters for lunch.
If CM is a must-do for you, but you'd prefer breakfast, I'd hold onto the reservation you have now and simply keep trying for an earlier one. With our 45 day mark coming up in about a month (you're going about the same time I am according to your ticker), there's bound to be a few cancellations.