Gerry:
I too will be coming from Dallas. Here's my suggestion.
1. Fly SW Airlines to Hobby.
2. Book the RT shuttle from Hobby airport directly to the ship via Galveston Limousine Service. http://www.galvestonlimousineservice.com/hobby.html , The shuttle costs $80 Roundtrip. The shuttle ticket counter is downstairs near baggage claim. The website will show the departure times.
Hope that helps. We have used this shuttle before and will be doing so again in November.