I fancy either taking a shot at
Tokina 116 as a wide angle
Or
Nikon 50 f1.4g
What do you think?
I think, I think like you

.
Manhattan is a great place for UWA photography (although I didn't have a DSLR when I visited some years ago

) and the Tokina is robust, discreet and very capable of being hand-held in the gloom and shadows (thanks to it's f/2.8 aperture). The good corner sharpness and lack of distortion with this lens are big bonuses too, as you might come back with a lot of shots of architecture and skylines.
If you want to travel light and avoid drawing attention from the 'wrong sort', taking the 50mm prime is also a smart move

. Having the possibility to shoot at f/1.4 is vital in a city (IMO), as you can't use a flash gun to illuminate such large scenes (well, only the foreground) and you'll get too much movement blur from the passers by and traffic, if you can only manage, say, f/4.5 :shrug:.
Yes, I'd take those two lenses and feel that I had 70% of the photo opportunities covered, but would be getting results that were 95% good. This would be more important to me than taking a slow zoom lens and being able to cover 90% of the required focal lengths, but ending up with only 60% of the images looking the way that I'd want them to :|.
Besides which, if you have a limit range of focal lengths, it can inspire creative solutions and more unusual pictures

. Let's face it - 'unusual' photographs of New York City are pretty hard to come by these days

.
Have a great trip and please come back and post us some pics!