Just coming back from a week long trip myself, in the end I left my Df home. Instead I took Leica X typ 113 and Leica X Vario with me. Out of those, the X Vario got about 95% of the shots. The 24-70 equivalent range of it's lens was fantastic for travel.
So with that in mind, travelling with the Df only I would also be inclined to go with 24-120 and maybe add a fast 50 like 50/1.8G to it. With that I'd be easily done. No lens changing during the day, just enjoy travel and sneak a few shots here & there.
Evening time swap on the 50 and go out for dinner & drinks..
//Juha