Today's cruiseships all handle rough seas quite well. On one of our cruises we encountered seventy mile winds and all the ship did was rock a bit.
Not to worry you will be fine.
Carnival Liberty New Year's Eve 2007
Liberty of the Seas 5/2008+11/2009
Allure 1/16/ 2011
Independence of the Seas 12/29/2013 Booked!