I second 6-2-6's recommendations of Napa Rose, Ralph Brennan's Jazz Kitchen and the Storyteller's Cafe. Try the oyster shooters at the Jazz Kitchen (I'm surprised 6-2-6 didn't mention these!). I believe there is a character breakfast at Storyteller's, but definitely go for the buffet (the prime rib is awesome).
Now, if you're in DTD (and you will be since you're staying at the GC), don't forget to hit Marceline's Confectionary (wonderful candy and cookie selections). Also, if you get in the mood for Mexican food, you can try Tortilla Joe's (El Rancho del Zocalo in Frontierland at DLR also offers some good Mexican food).
I'd also mention the ESPN Zone and Rainforest Cafe, but since you're looking for something new, never mind
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Have fun and be sure to tell us all about it in a TR when you get home.