re: Big Bend - half a day what would you do.

Santa Elena Canyon is probably the best bet. That area is one of my favorites in any national park. Hike into the canyon a bit.

If you still have time, you could drive into the Chisos Mountains. Lost Mine Trail is a shorter hike that you could probably fit into that timeframe depending on how much you spend at Santa Elena.

If yall want to get after it, Emory Peak is the tallest peak in the park, gives great 360 views, and is a fairly easy peak to climb. The last 50 feet are a scramble but nothing crazy. This trail is about 10 miles so you might need to budget 5-7 hours depending on how in shape yall are. Definitely a prettier trail than Lost Mine but Lost Mine is probably more bang for your buck, especially if the options are Santa Elena + Lost Mine or Emory Peak.

Marfa is cool, especially for the Chinati Museum. Amazing museum! Not sure how much is open right now though. Big Bend is definitely better to spend time at in general IMO.

Big Bend is truly a jewel of the national park system. Very uncrowded and amazing views is a pretty rare combination within the beautiful national parks like Big Bend.

The first 45 minutes of the movie "Paris, TX" are a good primer for the solitude and beauty of that area.