Even though RCCL probably won't turn your sister and her family away, from my experience RCCL has a much higher percentage of people who dress up for formal nights. Most men are in dark suits and probably 15-25% are in tuxes. Most women are in cocktail type dresses with maybe 25% in formals (i.e. long glitzy type dresses). It was much more formal than DCL's formal nights.
As for babies, I don't think you will have a problem. No, there will not be near the amount of children as on DCL unless you are travelling during a school break or summer. However, there was a baby (6 months) travelling with a group that sat near us when we went to Alaska and everyone made a total fuss over her the entire time (good type fuss!!!)
As for babies, I don't think you will have a problem. No, there will not be near the amount of children as on DCL unless you are travelling during a school break or summer. However, there was a baby (6 months) travelling with a group that sat near us when we went to Alaska and everyone made a total fuss over her the entire time (good type fuss!!!)