Do I need to get a special ATT package before I leave or is something offered to purchase on ship?
???? This is an old thread.
WiFi is free on the ship. You can use that to Skype or Facetime. Free WiFi may also be available at hot spots and business in some towns.
Your cell phone will work (for calls and data) when you are are docked or on deck at sea when near a town/cell tower. Service depends on your existing plan.
There is no need to buy any special phone or data packages for this trip with the possible exception of the Canada segment.