The Glacier Trip is a great idea but as another person said, finding a Hilton/SPG/Marriot/Etc hotel might be hard. Do you guys have good camping supplies? If so the mountain west is great for car camping and backpacking because of all the public land. If you are going to check out Glacier and Yellowstone I also think you should swing into Grand Teton which, imho, is much prettier than Yellowstone and has some awesome hiking. If hardcore backpacking is your thing then the Wind River Range in western Wyoming is amazingly pretty with less regulation than a national park.
Do you plan on driving up or flying? If you are driving up from the southeast, I would make sure to pass through Badlands National Park in SD to see a sunset/sunrise. I would also check out the Black Hill in SD, there are so many cool geological things to see in 'The Hills' it is about impossible to visit it all in a month, much less a few days. Custer State Park, Jewel Cave, Spearfish Canyon, Needles Highway, Deadwood, Devil's Tower, and to a lesser extent Wind Cave NP are all pretty cool. (Full disclosure, I am from SD originally so I might be very biased).
I wouldn't call any of these trips in my post Travel Hack Friendly, but they can be done on the cheap very easily if you are ok with staying at cheap hotels and camping to cut cost.