My go to kit for travelling internationally has always been the DA 15, FA 31, and DA 18-135. I very rarely bring anything else.
We've been to Iceland four times now (more to come soon) and I found that the DA 15 lived on my K-3, except for anywhere close to water. That is when the DA 18-135 came into play. The FA 31 gets used for museums, low light, and city life. I cheat though, because my wife brings her 18-55, DA 35 2.4 and my 55-300
... which she "forgot", which was too bad for all the eagles, seals, and swans, and ptarmigans we ended up seeing.
If I had the kit that OP has, I would probaby do the 15, 20-40, and 70. The only other thing would be the 55-300 if outdoor nature is going to be a part of the trip (as it should be).
P.S. WR is very important and do not go too close to the ocean