Now you are probably a far stronger cyclist than I am (wouldn't take much), but it might make for an easier tour if you used an MTB triple instead of the 105 triple. My bike was originally equipped with the 105 52/42/30, but I had it switched out to an LX 44/32/22 (required a new BB, too). The road triple gives you a 32x30 low, while the MTB triple gives you a 22x32. I was able to keep the 105 front derailer (for a triple). The bike has an LX rear derailer.

The LX crank is a few dollars cheaper than the 105, and the lower gears could make it a lot easier to tow a trailer through the mountains!