The most Eastern ports may be a little cooler in January, but still sunny and nice. Southern ports will be just right for a Winter break both air temp and water temp.
1. travel irons - NO ships don't want to risk a fire.
2. bringing your own champagne/wine- Pack it in your checked luggage.
3. What is "smart casual"?- nice neat casual attire: dockers and collared shirt for him, pants outfit, sundress, nice capri set for her. No shorts or tank tops please.
Have a great time.