I have read a fair amount on the subject but no one has touvhed on the Passport card. Gov website states its good for "entering the US from Canada, Mexico, Carribean and Bermuda at land border crossings and at sea ports of entry". Cost for 2 new adults and 2 new children for passports is $480, same for passport card is $190. I have also read that a valid birth certificate is enough but alot of ppl worry about what is probably less than 1% chance something may go wrong and actually need a passport. We have never had a passport and after this cruise dont anticipate needing one again before they would expire. So spend $$$ and be safe with an extremely small chance something goes wrong or save big $$$ and hope for the best. I really believe that a birth cert is enough but need reaffirmation. Also looking for anyone that has had experience either way.