Photo gear advice for upcoming road trip out west?

I'll let others address the question of what camera(s). Having been out that way recently, I'd say it's the little things that can make/break your experience.

Have a skylighlight/UV haze filter for each lens. I know a lot of people say to put as little glass as possible between the camera and the subject, but if a sudden wind kicks up, which would you rather risk getting dust pits on, the filter or the lens itself?

A polarizer and a graduated ND are in my "must have" bag for getting those great sunsets, clouds scudding across deep blue sky, etc.

A puffer or rubber blower and a very soft brush. (That cussed dust!)

A decent flashlight or headlamp (my preference) to find your way back to the car after you've shot that gorgeous sunset. It gets mighty dark mighty quick out there. Also useful when setting up for some night-sky photography which I guarantee you will want to do.

None of the above will add significant bulk or weight and I'd bet you will use them.

Have a wonderful trip

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Gallopingphotog