Reliant is about 1/2 an hour from NASA. The Aquarium about 15 min, but it's not that special although does have white tigers if you have never seen one in person.
Other suggestion is Rockets game either Wed or Fri. Texans play SNF vs Colts if still in town.
If you have Rented a Car and in town until Sun, maybe drive to Austin (2 hours) for UT Kansas game