First thing I would do would be to go to an Academy store and get a TOP SPOT map. Our offshore fishing in the summer can be really great. King Mackrerel, Dolphin, and Cobia can all be caught from about May to Sept. Kings and Dolphin are taken by trolling or drifting baitfish. If he has culled recently, this can produce some excellent king fishing. For Dolphin, try trolling along weed lines.
Bottom fishing is usually for red snapper on banks or around platforms.
If all else fails, trigger fish and spade fish are usually plentiful around platforms anywhere from 10 to 50 feet deep and can save what would otherwise be a skunked trip. I don't fish offshore much in the winter as the kings, dolphin and cobia are gone. However I have caught bullreds, snapper and large white trout around platforms during the winter. With a 19 footer, fishable days are few and far between until about April. Incidentally, Galveston has some good Tarpon fishing in the summer within a few miles of the shore.