Matt,
I would suggest bringing the 5x7. While you have an ambitious travel plan, I think it would be good to occasionally slow down and appreciate the light in a way the Large Format encourages (though of course one can appreciate the light without LF) -- especially since you have professed a liking of AA.
If you just set the 5x7 up once a day...or even once every other day...it will be worth the extra bulk.
If you are in Yosemite on a Saturday, the Ansel Adams Gallery gives a talk on AA's work and shows his prints -- check the day before to make sure there is space, as it is a small group (while there, you can ask to see work by others, such as Kerik's...and some of mine).
If and when you came through the the Redwoods (Redwood National and State Parks), and you need a darkroom or suggestions, let me know. I am in Eureka. But you might find that we are a bit too far to the north if you are planning on the Grand Canyon, Yosemite and all.
Vaughn
PS...whoops, I shoud have reviewed your plans...you are not heading as far east as the Grand Canyon. Enjoy your trip!