Last year I went on a 3 week tour with a 52/39 crankset paired with an 11-34t cassette. We only hit one hill I had to walk but that crankset was still a bad decision. In the end, though, I'm all about touring with what you've got. This year I've got a road triple; still not as low as I'd like, but it's what I have lying around at the moment.

If I weren't saving all my money to fund the tour I would be all over that LX crankset from Jenson. If you're running a friction front shifter I say buy the LX and a matching FD. It'll only set you back around $120-130 and with the right cluster in the rear you'll have pretty much the lowest gearing possible.