Hi northerner, restarants in Ncle are one of my fave subjects, not that i get to sample them much any more!
I'd recommend in city centre/quayside:
Cafe 21 on Queen Street, classic, french, lovely food and great service and wine but not stuffy.
Paradiso, italian/mediterreanen (sp)food, you could ask for the upstairs room and sit by the kitchen or the private dining room. Lovely staff again. Also has a deck area outside so maybe you could have a pre dinner drink here. I love it here and big fave for work lunches. Also above a great bar, Popolo, owned by same people and has big cocktail list. Restaurant not as classy as some of other on this list tho.
The Apartment on Mosley Street - chic, a bit posey, almost footballers wives but classier! You'll probably spot a local celeb there. Great reviews, you'd need to check if they can seat 30 tho.
El Coto on Leazes Park Road, again medit type food and tapas. This is quite new and heard good things about it. Also have a private dining room. Also a courtyard area, agin for pre-dinner drinks.
Out of town a little (a mile or so): Barn @ the Biscuit - ever popular restaurant used be where El Coto is now but now in old biscuit factory converted to contemporary art gallery.
Fisherman's Lodge, Jesmond Dene - Upmarket fish restaurant in the Dene so feels like out in countryside.
At work so will try and post numbers for these later. HTH to start off with.