If your vacation time is flexible, consider yourself fortunate. You have the ability to choose to cruise when prices are lower and cruise ships are generally quieter. There will be far fewer children to compete with, and ship activities will be more enjoyable. In the Caribbean, for instance, the highest prices and larger crowds occur during mid summer, school breaks and Christmas week. By choosing a cruise in, say, early November, you'll save money and easily navigate the ports and biggest attractions with fewer crowds and more elbow room.
For more on the subject of when to cruise where, see my article: Destinations and the Best Time to Cruise Them