What's a good place for a family lunch in NYC?

We’re taking the kids (ages 6–12) to NYC for the day later this week. Our plan is to first visit the American Museum of Natural History, have lunch, visit the Lego store (Rockefeller Center), and basically just wander around to see the sights before taking the train home again.

We don’t usually take the kids to the city, so we’re not sure where we should have lunch with them. Someone suggested Mars 2112 as fun for kids but said the food wasn’t that great. What are some other lunch spots that wouldn’t be out of the way for us (or cost an arm and a leg)? We have one picky eater, one with normal kid tastes, and one that will eat just about anything.