Houston weather is hot and humid this time of year, so we recommend lots of athleisure and lots of linen for the day time. Also, a good SPF and bug spray or lotion are great to have when outdoors.
Many major airlines fly direct to Houston, and IAH or HOU are equidistant, roughly, from the city center.
Uber and Lyft make it easy to get around so you won't need to rent a car, but all major rental companies are at the airports, or Turo is a great option as well (rent from a car owner).