It may be a long hike for smaller kids, but we've seen a lot of families on this trail.
Huntsville State Park is straight north of Houston off of I-45. For this trail, it is best to start at the nature center. Grab a trail map as the pegs on this description are not perfect. This trail follows the Orange Trail on the state park map. Take the Chinquapin Trail north from the nature center for a nice counter-clockwise loop around the lake.
There are a lot of side trails in the area just north of the nature center so keep an eye out for the orange blazes. The Chinquapin trail shares various sections with the Triple C Trail that follows the perimeter of the park. This trail is a service road built by the Civilian Conservation Corp (CCC) as they constructed Huntsville SP. There is a dam about 2/3 of the way around the lake that can make for a nice picnic spot.
Trail signs are are in plentiful supply and easy to see. Be sure to follow these as it is easy to get onto another trail. One of which is a trail that leads out of the park.