Hi there.........I'm a mom of 2 boys, ages 15 and 16 (17 on Friday!!!). Anyway, I don't like their "style" either, but when in comes to dinner wear, ie, docker type pants and dress pants, I have the final say. We buy the right size and they wear them. Have your boys tried to wear oversized "dockers" or dress pants.....they'll see, they really aren't making any kind of fashion statement., it just looks dumb. Side note........my son just went to his Junior Prom and I went to take pictures of him and his friends; 20 couples, the boys looked fabulous in their well-fitted tuxes!!!! So anyway, put your foot down for the dress up clothes and don't worry about the other stuff. Also, let them know that most boys will be dressed like them, and that right after dinner they can run back to the cabin and change!
Good luck and happy cruising.