Welcome aboard the RoadTrip America Forums!
By the most direct route (I-45 and US-287 up to I-40), the Grand Canyon is just 2½ days from Houston, So if you plan to spend a day at the Canyon, you have another day to sprinkle on detours and at stops along your drive. What I'd suggest is that you look at a completely different route either to or back from the Canyon that satisfies your desire to see some of the 'wild west' and use the short route the other way. One possible alternative would be to use US-90 and its extensions. Say, take US-290 through Austin to Junction and then head down US-377 to Del Rio and US-90 along the Rio Grand through Langtry (Judge Roy Bean territory), Marfa (site of some strange lights in the sky), and hook up with I-10 at Van Horn. The last leg would then be US-191, the scenic Coronado Trail up through eastern Arizona to the Petrified Forest and the Grand Canyon.
If you plan to star gaze, there are two things you should bring with you. A star map for the time you'll be traveling and a pair of moderately powered binoculars if you have them. Neither is absolutely essential, of course, but they will add immensely to what you can see and learn from the clear skies of the southwest. And to both be out under the stars and to save money, you might want to look at camping in state parks a night or two, particularly when your route takes you well away from civilization and the Interstates on a given night.
AZBuck