I asked my 12 and 10 year old their favorites and why, and this is what they said:
1. SpaceCenter Houston - Though my kids did not grow up in the era of "Houston, we have a problem." or the Challenger disaster, they were so very interested in the history of space exploration and really enjoyed SpaceCenter Houston. Along with tours of Johnson Space Center, there are plenty of hands on exhibits and movies to see that really teach the kids all about NASA and space exploration.
2. Kemah Boardwalk- Very close to SpaceCenter is the Kemah Boardwalk. It was a great place to go to after a full day. We walked around, played games, rode fun rides, and had dinner. If you don't have time to go to the beach while in Houston, this is a great place to go, situated right on the bay - we saw fish, jellyfish, boats, and more.
3. Houston Zoo- The Houston Zoo is very shaded and a great place to go anytime of year - don't let a summer month stop you. It has some really great animal encounters (the day was packed with them) and we really enjoyed some of the unique ways to see the animals (my kids loved the fish tunnel). They also have a great splash pad and a wonderful Children's area. Don't forget to ride the train that sits right outside the zoo.
4. Houston Children's Museum - The Houston Children's Museum is one of our favorite children's museums we have visited. Hands-on fun at Kidtropolis and Invention Convention kept us busy for hours. We also really enjoyed getting wet at the outside FLOW exhibit. You could spend all day here and still not see it all.
5. Houston Museum of Natural Science- Now normally my kids wouldn't think that a science museum would be amazing - but they thought the Houston Museum of Natural Science was. They really loved the dinosaur exhibit - there were rooms and rooms of full-scale dinos to see. They were also fascinated by the Hall of Gems. And the museum has a planetarium and an IMAX theater as well.