My child also would cough for weeks after a respiratory infection and well after the contagious period. However, with going on a cruise I would definitely have a check up beforehand and maybe do a repeat covid/RSV test. As someone else mentioned, you do have to fill out a health screen (always have, basic questions like has anyone had diarrhea or vomiting in the last 2 days, etc). Depending on what you answer you may have additional screening.Of course people lie all the time, but that’s on their conscious. Now if your kid is hacking away at checkin and sounds like a lung is coming up, they may pull you for additional screening.