Hi there. You still have time to get the big FREE book about TX, I think it is put out by the TX Transportation Dept., or the TX Tourism place. I'll have to find mine, and look.
Go to the monthly magazine www.texashighways.com
you will find out a lot of info. Look at previous issues, too.
How can anyone start to tell you about the sights to see, and the different terrains there are in TX. Each area of TX is so different from the rest. Forests, lakes, plains, mountains, deserts, beaches. Whatever you want. Like they say, "It is a whole other country".
You didn't forget to put San Antonio on your itinerary, did you ? The River Walk, River Boat Ride, Alamo, etc. Then the Hill Country, nearby.
Hope you have a great time here.