I am kind of concerned about the info being passed around on this board.
As a general rule, even if you are taking your own kids and dad is staying at home, it's always best to have a notarized letter from dad saying that you can take
his kids out of the country.
It has more to do with homeland security, not the cruise line.
If you look at the other cruise line's web sites, they state that notarized letters may be asked for in the ports. Doesn't Disney provide the same advice?
I am an active member at cruise critic and we discuss this issue all the time. Some parents have been asked for the letters and stopped by the port officials, not by the cruise lines.
My kids have the same last name as me. They have passports. But when we travel without my husband, I bring a letter saying I have his permission to leave the country with his kids.
Maybe since Disney traditionally doesn't go to some of the ports that have more strict guidelines, like Mexico? But when they start doing Mexico regularly, Disney will have to follow that country's rules.