If you are willing & able to spend a little more, Disney Cruise Line would probably fit the bill for your family. They are wonderful for kids of certain ages (5 and 10 being among them)! Check out my review on cruisereviews.com of the Disney Wonder, and feel free to email me later if you like, with questions. (Disney does offer a 7-day cruise, in case the shorter cruises don't appeal to you.)
That said, many cruise lines offer good children's programs, Royal Caribbean & Carnival among them.