From TV ads you might believe that cruises were for middle-aged and older couples, happy to pack evening wear so they can dress for dinner; hardly the sort of holiday to take a wandering one-year-old, naughty nine-year-old or troublesome teenager. Step up Royal Caribbean’s Symphony of the Seas where, as I discover on a special pre-launch cruise, kids of all ages, parents and grandparents, can holiday together but not stick together, a truly multi-generational destination.