Best sushi on property - Kimono's at the Swan (but they don't accept the dining plan). Morimoto's in DS is also good. If you are looking for something in a park, as PP said, the QS place in Japan in EP has a small sushi item on the menu and it's fine.
Lamb - I would suggest Spice Road Table in EP. The food is delicious and the have a great lamb entree. If they would like something smaller or something to share just to try lamb, they have great lamb sliders (you get three sliders with the order).
There aren't any traditional chicken and waffles in WDW. Closest thing would be the sweet and spicy chicken and waffle sandwich at Sleepy Hollow in MK.