Hi, going on first cruise in Sept (Carnival Paradise). Have heard about drink coupons you can buy ahead of time (group of four for $19.75). I'm wondering if this is correct. Can you use them for any drink (even the fancy, fruity drinks that I love)? Can you only buy them before the cruise? How do I do that? It sounds somewhat appealing but I don't know if it is worth the hassle. Any advice?