How about Mama Fu's in Times Square
East 6th Street for Indian - very cool, very very cheap, and delicious
Carmine's is an old time favorite for italian, it's family style
White Horse Tavern (burgers, etc. history, a NYC landmark)
Check out
www.zagats.com and/or pick one up when you get here - it will list all the best in a variety of price ranges
And, don't forget the old stand by cheap lunch hot dogs
Also, there are some really neat hidden places, can't think of the name - but what is the one up on East 50th that is like a haunted house??? is it still there? it's a fun experience
Also, try something for dinner that has entertainment, like a cabaret place
And of course if you want the NYC night out thing you can take them to Tavern on the Green (how is that these days NY'rs?) followed by a horse and buggy ride!