Welcome to the forum
D5100 is in my book a bit obsolete body, however it is doable! If I was you I'd consider renting a body+wide angle for iceland, and then buy a 50mm prime.
The D810, if not too expensive, would be a good choice, yet D610 will be plenty.
Why the pro lenses? Iceland can be crap weather from start to end of your trip, and weather sealing isnt a concern in the pro bodies.
Hope you have a nice trip.
Tamron 15-30 or Nikon 14-24