L.P.
I second Amanda on Galveston and San Antonio. We've done both this time of year. San Antonio is great for the history, River Walk (great restaurants) and we saw Wicked at the Majestic, it was fantastic!! Galveston is a quick way to catch the sight and sound of the ocean, great seafood and mexican food. Yes, I frequently plan trips around eating!
For smaller town, simple vacations, check out The Villages outside of Tyler. Gorgeous wooded settings on Lake Palestine. You can really unwind and spend some quality family time and Tyler is just minutes away with movies, restaurants and shopping. Beaver's Bend in Oklahoma has been recommended to us, but we've never been there. I've literally taken a map and drawn a circle that encompassed the distance we were willing to travel and just checked out what fell inside the circle. Discovery can be fun!