My father-in-law is hoping to be able to take my mother-in-law on a Caribbean Cruise for their 50th wedding anniversary (coming up in 3 years). They're saving up for it, and there has been a lot of family interest among my husbands aunts and uncles about possibly going at the same time. If they get a large enough group of people going, will they be able to get a group discount? There could possibly end up being 20-30 people going on the cruise. Also, any "do's and don'ts" tips for cruises would be appreciated.