As a parent can quickly grasp, Houston is kid-friendly. Easily half of the listed attractions are geared for kids or have a large component especially suitable for them.
A tour of southeast Houston will take you to The Orange Show, with which young kids display an almost instinctual connection; the boat trip on the Ship Channel; a visit to the Battleship Texas; and the wonders of Space Center Houston. After that there's a visit to the boardwalk in Kemah or a trip to the beach or to Moody Gardens in Galveston.
South of downtown you have the Museum District, which includes the Children's Museum, the Houston Museum of Natural Science, and the Museum of Health & Medical Science. And, of course, there's Houston Zoological Gardens, which has a special children's zoo that explores the different ecological zones of Texas. To the north is SplashTown, a water park, and to the southwest is the George Ranch Historical Park for kids interested in cowboys and the Old West.