how can i find deals for a disney cruise vacation for a family of 5?

Have you check at http://www.cruisedeals.com? Yes, passport or passcards will be needed. Passcards are cheaper than passports, but they only allow travel to Mexico, The Caribbean(bahamas), and Canada so you could do this.

Sometimes the closer you are to the date of departure the cheaper the cruise, but you would be pushing your room choices.