Hi Joseph!
While technically, the United States does not require passports for your cruise leaving Port Canaveral and heading to the Bahamas, I think its a good idea to go ahead and invest in them.
We recently sailed on the Disney Wonder and our family chose to get passports for the following reason: If there is an emergency which requires that we return to the U.S. via air, passports will be required. This could happen due to a medical emergency, missing the ship when returning from an excursion, an emergency stop in a foreign port - a whole host of reasons. For peace of mind, there really isn't any other option than having your passport as backup.
For current passport requirements, be sure to visit the U.S. Department of State's website at www.travel.state.gov or call the U.S. National Passport Information
Center at 877-4USA-PPT.
More information can also be found under the Disney Cruise Line's
passport information pages.
Hope this helps! Bon Voyage!