First, some questions: Where is it that you'll be travelling to? How will you be travelling? What is it that you are keen to photograph?
In any case, my answer is likely to be the following: If you already have a 24-70 then I think you don't need to look too much at other options. The 24-105 with IS is another versatile option with a bit more reach, and then there's the IS vs. extra stop debate, which for travel, good IS perhaps wins, but despite those two factors, I wouldn't worry about changing your lens. I base this on the fact that for the first few years I lived in Spain I was using that lens when travelling around and it was ideal.
Some would argue that 24mm isn't wide enough, and I will say that there are times when there isn't enough room to fit a whole cathedral, or tower, or what-have-you in the frame from the very bottom to the top ... however I'm not really into that anyway, so for me it wasn't a biggie.
I'll post a couple of sample albums from travels with that lens, these are from Bilbao and Donosti (San Sebastian) in the Basque Country (Northern Spain) ...
One more from the North-West tip, Galicia ...
All the best,