As both Lakeshore and UncleVanya suggested, the K10D and kit lens may be plenty. (unless your companions are indulgent of your photography hobby).
At the suggestion of several here, I tried stitching with a simple program like
MS ICE. You might try a little practice with this program and your kit lens before you leave and see what you think. I found that pretty decent images are possible with hand-held shots and stitching them together to get a wider angle view.
Aside from that, I have both the Pentax 12-24 and the Sigma 8-16. They aren't identical in use, but they overlap enough that I don't usually carry both at the same time. I feel the Pentax 12-24 has the edge in IQ, but Sigma has that extra coverage that is sometimes indispensable. Wide angle would be my biggest suggestion for a different lens if you don't want to take multiple images and stitch.
But really, if you can swing it, pick up a lightly used Pentax K-5II or K-5IIs. Great image quality for a good price these days. I agree with that advice. And with those who say a lot of kit on a general travel trip (as opposed to a specifically photography-oriented trip) is more of a pain than it is worth. A couple suitable lenses and the best body you can bring along.
Enjoy the trip and let us see some of the results!