I would see
Glacier
I know you wanted some more information so here goes. I have driven out there twice from DC to go back packing and we did some small day hikes as well. For day hikes there are tons of circuits trips in Glacier. it has over 700 miles of trails. Whats nice is there is the Going to the Sun road, which in itself is a must see. The road intersects the park across the continental divide. The park has free buss services all along the road so as a hiker you can get off and on wherever you want. That opens lot of day hikes and longer if you wish. Shuttle time use to be 30 minutes.
For hikes I would do the Garden Wall hike from Logan Pass to
Granite Park Chalet. and then down to the loop. Take shuttle back to Logan pass.

The Challet is one of 3 back county, "hotels" you can stay at, but booked for a year or two lol. Hope you don't mind heights.
Up from the Campground at Two Medicine to Dawson pass and hike the continental divide to Cut bank pass and then back down to Medicine.
Those are just the two day hikes we did lots more to do. Check out the
map.
BTW ever thought of taking the train? You can hop on the
Amtrak Nation Builder in Minneapolis and g right to Glacier, 3 stops and continue on to the west coast if you want and fly back. YOu can rent a car at the East and west glacier Driving back sucks .