As most have said, it really depends on the child and what stresses out the adult. We booked a 7 day on Fantasy last September for myself, wife, 5 yo daughter and 18 month old son. We took a family beach trip to Florida in June before the cruise, and as soon as we got home, we called and cancelled the reservation for our son, and decided he would stay with grandma. He did not care for pools and did not sleep well away from home, and basically one of us had to stay in the condo with him most of the time in Florida, and we did not want it to be that way on the cruise. We also didn't want to take him and then keep him in the nursery a lot either. That being said, we had a great time with just the 5 y/o and found lots if time to relax while she played in the kids club, which she loved. Not sure if that helps, but that was our experience.