Vibration is your biggest problem. With Nikon Pro lenses like the 70-200mm F2.8 VR then you have two settings normal and active of which active is for moving transport which you are on. If you don't have one of these then a normal VR lens is better than nothing. Might have to raise the ISO and shutter speeed to get a decent shot but it all depends on the brightness of the city below. Try you camera out in your street at night and see how it preforms. Also, increase your exposure compensation to plus 1 or 2 and see how the images turn out. Practice before you take the trip so at least you know which camera setting might give you the best results. At least, Las Vegas at night is the brightest city in the world, so you stand a chance of getting some great shots.