My example was to show that if you are new, and going on a trip, you can get nice scenic shots using the "kit" lens. I shot that only having the camera for about two weeks. Sure a basic understanding of photography helped...but you will do well with it on your trip. If i recall correctly, I used 18mm at f/8 or f/11, I forget. I did crop a bit 'cause being a noob I put horizon dead center, so I cropped for that, and adjusted in raw for lens correction, cloned out a few bug circles in the water, but thats about it on the PP side of it.
as for the zoom...depends on your budget really. if you can afford the nikon 70-300 vr II get it, it's nice. If you can't, tamrom makes an ok lens for the money spent. Sure there are others, but those are the only two I've used. IMO you don't need fast zooms as you are not really ready to use them to their full advantage.
I printed that one and sold two at 12x18, looked great. and since we have our new printer up and running for large prints, I am going to print 24x36 to hang on the wall for a sample of our large prints...I won't need to do anything to it, so if you are concerned with printing, don't be. If you get a decent, well exposed, non blurry shot, the d3100 and kit can produce 20x30 prints with ease.