DO NOT DO THIS. YOU'LL BE SORRY.
Go to Fields (nice) or Frenchglen (awesome) and park the Airstream. I highly recommend the Frenchglen Hotel!! After parking your baby, take your truck up Steens Mountain. You do not, absolutely not, want the Airstream up that mountain and back, unless you intend to wreck it and file an insurance claim.
Besides other trips, I honeymooned there some years ago, early September. At the hotel it was still late summer. The valleys halfway up were late autumn. On the top of the mountain the snow was as deep as my 8-inch boots. You could stand in the snow, look down at golden trees in the valley, and see summer off in the distance.
What you mostly see, though, on Steens Mountain, is white-knuckled big-eyed drivers inching their way along in the other lane, wearing Illinois plates. I am not kidding.
Sure, you're from Oregon and you "get" this, but Steens Mountain is nothing like Mt. Hood. Just don't.
This is
not at the top:
The area:
DO NOT MISS the Alvord desert. Stop at Frenchglen Hotel and the café at Fields. If you flyfish, try the Donner und Blitzen (thunder and lightning) for some of the most gorgeous trout on earth. Go see the Pete French Round Barn. Note that what some in the West consider the only "real" wild mustangs are in the Kiger Gorge.
Read this:
http://www.oregon.com/recreation/steens-mountain
And this:
http://oregonflyfishingblog.com/2011/08/01/the-steens/
BE PREPARED FOR ANYTHING weather-wise. Seriously.
Also be prepared for this: