Ash31092:
Club O2 is a great way to keep teens happy but...I think the age limit should be 15-18. 18 year olds have more fun with that age group rather than older adults.
The trouble is that 18 year olds are adults, and Carnival would be opening up itself to all sort of problems if they allowed adults to socialize with children.
As 18 year olds, IMHO, one is old enough to start making one's own social circles. You shouldn't be needing Carnival to do it for you. When on board, seek out other 18, 19 and maybe even 20 year olds, and organize your own fun.