I can't help you , but I'll be watching for experienced cruiser's answers! We'd love to fly to Europe and cruise back, but the cost of flying is more than the cost of the cruise ! One way flight's are ridiculously priced, IMHO.
"A truly happy person is one who can enjoy the scenery on a detour."
Carnival Inspiration 2002 Carnival Elation 2004
Grand Princess 2004 NCL Sun 2005
Sun Princess 2006 NCL Dream 2007
Caribbean Princess 2007 NCL Dawn 2008
Island Princess 2008 Island Princess 2009
Golden Princess 2009 Carnival Conquest 2010
Grand Princess 2010 Island Princess 2011
Grand Princess 2011 Carnival Magic 2012
Carnival Dream 2012 Island Princess 2013
Carnival Magic 2013 Carnival Legend 2014
Sea Princess 2014
If you are happy to change in Europe, then both Amsterdam (Schiphol) and London (Heathrow and Gatwick) have several flights a day from Venice, and then on to Houston. This includes budget airlines such as EasyJet, RyanAir or Transavia, KLM, and BA (If they are not on strike).
So look for a few routes, then shop around on line options.
Alan & Katrina
Last Cruise: Azamara Journey August 2014
Next: Queen Victoria November 2014
Followed by: Queen Elizabeth December 2014 and Minvera April 2015
I think this is the one situation I would check and see what the Cruise's air fare is.. They may be able to get certain breaks for a one way ticket...Be sure to check with the airline too and see if there is a difference.