Heya,
Well, night photos require either long exposure (tripod, which can be a tiny one, or little bean bag, etc), or wide aperture. I assume you mean night sky? If that's the case, you need both wide aperture and long exposure. The 18mm end of your kit lens at F3.5 is ok, but really, wider is better here and faster is better here, F2.8 should be a starting point.
Sounds like you want macro & telephoto as well. Those are easier to fit the bill with, on a crop, than ultrawides. Unfortunately, you cannot really have an ultrawide for landscape, a macro, and a telephoto and keep it as 2 lenses. The only way to really do that, would be to use extension tubes or a clip on diopter to make a macro lens on the fly out of one of your lenses.
Here's what I'd do:
Night/landscape: Rokinon 14mm F2.8, and take a little bag that you can fill with sand/dirt to act as a make shift tripod for long exposures, unless you want to carry a small tripod.
Wildlife/Macro: Tamron 70-300 VC. And carry around a Raynox DCR-250 clip on lens, which converts it to macro on the fly by clipping the lens on the front. Drop her back to 70mm to 100mm, and you're set for macro. You will just need a lot of light, or take a small flash. I imagine you'll want to do natural light. The alternative is to carry a 3rd lens.
As an alternative, you could get a 3rd lens. Get a macro lens. EF-S 60mm is a good one and not too big. I find the Raynox DCR250 ($75) plenty good enough for walk around macro, if you're not into dedicated macro anyways.
Very best,