Just got back last Friday!
We really, really loved the America restaurant at NYNY--it was a pretty casual spot, not quite a coffee shop, but not really like their other sit-down places. They had a huge menu of all sorts of food from different parts of the US and it was all great. They also have this huge sculpture-type thing of the lower 48 states suspended from the ceiling. It's really fun to look at while you're waiting for your food.
We loved the La Creperie at Paris--fabulous crepes, both sweet and savory.
We thought the Flamingo buffet was really tasty and a great value. We got a window seat overlooking their flamingo habitat.
We had an awesome lunch at Top of the World at Stratosphere. The day view was really neat and our lunch was very good and very reasonable. If you dine there you get free access to the observation deck. They offer dinner, and I'm sure the lights are incredible, but they enforce an informal dress code for dinner and we didn't have the right clothes.
There was also a sandwich shop at MGM called WichCraft which was very tasty--kind of like Earl of Sandwich.
If you have any Star Trek fans in your group, Quarks at the Hilton was a lot of fun. It was overpriced, but you're paying for the atmosphere.
Hope you have fun!