I love it that people ask me for dinner ideas. My friend Sara's mom was visitng recently, and Sara needed somewhere to go with her mom and her mom's friend. The parameters were: Union Square area, not too crazy expensive, parent-friendly so not too annoyingly hip and sceney, but New Yorkish enough to give the midwestern ladies a thrill. My ideas were the following...
Basta Pasta - really cool spot, an Italian place run by Japanese. It's got this interesting cross-cultural approach, always lots of expat Japanese there, Italian food through an Asian lens. Not too expensive, on 17th at 5th ave.
BLT Fish is great, on 17th street, a casual (no res) fish shack downstairs, a more upscale and expensive dining room upstairs.
Mesa Grill might be good too - very parent-friendly, southwestern/mexican food, upscaled. The celebrity chef factor might have some appeal if she watches the food network. On 5th Ave. at 16th or so.
There's a newish tapas place, big and glam spot called Barca 18, on Park Ave. South at 18th St.
Beppe - I've heard great things about this place, mid-range Italian, 22nd street at Bway. [This is where they ended up going, and they LOVED it. They had to wait for their table for a while, and were comped free champagne and fries while they sat at the bar. I love it when a restaurant realizes they need to placate the paying customers. I mean, my friends won't remember the fact that they had to wait 40 miniutes for their table, but they will remember the free goodies and the fine treatment by way of apology.]
Also on the same block as Beppe is a prix fixe spot called Kitchen 22 - $25/3 courses, supposed to be really good. But I did hear that they recently had a change in chef, so no telling what it has become of late.
In the ABC Carpet & Home store are a couple good restaurants - Pipa, which is tapas (never been), and Lucy which is upscale Mexican (where I had a very good lunch once, though it may have been distorted by the fact that I had just come from the dentist and my entire mouth was numb.)