Four of us will be cruising on Mariner of the Sea - never cruised Royal Caribbean.... we have an Ultra Spacious Ocean View room... Only 1 of us drinks alcohol - the other 3 are considering buying the non-alcoholic Beverage Package - however, if the 4th person gets the drink package will we all have to get it? We do have an 18 year old with us and she may want a drink - does her mother have to sign a waiver for her? Also, how much is a single drink? Thanks for your help and answers.