in my opinion you're more likely to get the chance to go to DC than on a cruise, take the cruise, i've been on 2 and its always a blast, as to which line, do your research, find out whats on the ships, what is there to do. Cunard is more an adult oriented line, where carnival is focused on the family with tons of things for kids plus private areas for adults to go too, so i'd take the cruise and more than likely take a carnival cruise, i haven't been on one to speak about it, i've only been on Norwegian Cruise Lines, and Disney Cruise Line.