Thanks for all the great advice!
I have about a year to think about all this and my mind changes about every day so we'll see.
I prefer a hotter climate, so the humidity and heat of the Caribbean don't really bother me that much. My fiance's family as well as my own mother just got back from cruises to Alaska (one on Holland America and the other Princess) so I'm not exactly dying to go to Alaska since everyone else just got back and weren't all that thrilled with the cruise.
I'm working with a travel agent but she didn't seem to know all that much about the climate in the Caribbean in August so I'm curious how others have felt about the weather at that time of year.