24-105 f4 IS, 70-300 DO IS (or the non DO 75-300 IS, I'm not a fan of white lenses) and the 28mm f1.8 would be my choice. I'd only take the 75-300/DO for Iceland, for city based images I'd just use the 24-105 during the daytime, and the 28mm at night to keep things less conspicuous.
Iceland is very dim during winter. I'm equipped with primes only because of that. But having only two primes may be a bit too limiting. If I could only have two lenses to live with for all situations I would probably pick 24-70/2.8 L and 200/2.8 L. 24mm is pretty wide on FF and the 200/2.8 L takes teleconverters without too much hit.
Another option might be a 16-35/2.8 L, 50/1.4 and 200/2.8 L. It's three lenses but the 50/1.4 is small. A friend of mine was in Paris lately only with a 20D and 35/2, shot great images and told me the added low light capabilty of the prime made fully up for not being able to zoom.
