They are open for lunch during the August/September free dining period. Yes there will be characters. I believe the menu is the same as dinner but I will move this to the main restaurant board as reservations is really not the place for it.
If you call the dining number, they can tell you what the menu is. The last time I asked, it is different than the dinner menu. Lunch, for example , does not have carved meats, but they do have cold cuts. The CM I spoke to at the time said to compare it to the Crystal Palace's difference between lunch and dinner.