Thanks for all the input! We still haven't solidified any plans, but we have an idea of what we're doing now. I hope! My sister and brother in law will be moving to Montana in a couple of months (we're in Michigan). We knew this was in the works, but didn't anticipate it happening until next fall. So! We're hoping to drive out to see them mid-July in combination with a visit to Yellowstone (they're a couple hundred miles from the park). This means a shorter visit to Yellowstone than we'd hoped, but as everyone has pointed out, this isn't a visit once kind of place. Down the road we'll plan a longer stay and do it far enough in advance to book the Old Faithful Inn (that's the most desirable one, right?). On this trip we're hoping to get in some fun stops on the way out or on the way back. Any suggestions would be welcome!