you might want to check the map. Dallas to Galveston is a 5 hour drive for most people.
Houston, however, is a hour away. Quality Arms, Collector's Firearms come to mind. There's another big gun store south of Westheimer on Hwy 6 ( west side of Houston, s of I-10), but the name escapes me.
in that same area is (was? i haven't been there in 8 years) American Shooting Center, with plenty of rifle/handgun, skeet/sporting clay ranges.

“When faith is lost, when honor dies, the man is dead” - John Greenleaf Whittier