While there are many characters in all 4 parks, not every character has a meet and greet (some are only in the parade and shows, others do not meet at all)
My cruise in 2012 was the "Hurricane Sandy" cruise. We wound up not stopping at Castaway Cay, plus the last night was extremely choppy. Didn't stop me sailing in the fall though (9 of my 11 cruises have fallen during hurricane season)
I am. Sailing on the Magic next month, and it will be my 9th Halloween cruise (favorite character interaction would probably be meeting the "Sanderson Sisters" on the Wish last year)