We've done quite a bit of cruising, and while we don't have young children, we've seen many traveling. We haven't really seen any in shorts. The minimum that I have seen for boys would be khaki pants with a short sleeve shirt, and skirt and blouse for a young girl. You can go to the other extremes of an 8 yr. old boy with a Tux on a 2 week Panama Canal cruise, and 5-6 year old girls with gowns. Hope this gives you an acceptable range.