“Covid 19”

My son tested positive last thursday for covid 19 and it is now the following thursday so it has been 7 days. He has been symptom free, no fever, for 5 days. We are supposed to go on a cruise on sunday which will be 10 days. We took an at home test today and there is still a very faint line. But since he has been symptom free does that mean he is not contagious? I have heard that people can test positive after having it for weeks. We are just really excited to go on our cruise but don’t know if he is Covid free yet.