La Tarte Flambee! Sandra and I have done a lot of damage there. smileys/wink.gif 2nd Ave. b/w 90th and 91st. >>>
Cheap. Cozy. Great flatbread pizzas. Given that you can walk a city block in about thirty seconds here, it would take only a brief stroll to get there, really.
The Czech Cultural Center (73rd b/w 2nd and 3rd?) has a fancy (nice, and well reviewed) restaurant, if they're looking for something unusual. Lots of great patisseries--Maison Kayser, macaron places, etc.--in that area, too.
"Rock of Ages" is playing on W. 44th b/w Broadway and 8th, so the theater district/Times Square; in my opinion, a dead zone for actual food. Cafe Un Deux Trois is at 123 W. 44th (b/w 6th and 7th), but I only recommend it for the ambiance (serious old-world French brasserie vibe) and drinks, not the food (alas). (They did, however, once have a decent apple tart.)
There are some great places on 9th Ave if you just kick around there in pre-theater mode (i.e., Vietnamese around 9th and in the low 50s). Nizza on 9th is our go-to for French and Italian--reservations necessary.
If someone asked me where I'd want to go to dinner for a splurge, however, I'd probably say Boulud Sud (still haven't been--Bar Boulud is nice, though--both near Lincoln Center), or Bistro la Promenade (Chelsea). For pre-theater, I'd eat outside the theater district/Times Square and just count on hustling by foot to the theater (it's faster to walk than take a cab in that area around curtain time), or taking the subway.
A trip to Chelsea Market (14th St. and 11th? 10th? Avenue) might be in order if they like (I hesitate to use the word) foodie-oriented jaunts....
Sorry this is so discursive! My brain feels like Swiss Cheese, these days.
Richard would be able to make more recommendations....