I wouldn't recommend a Carnival cruise in the summer -- unless you like being surrounded by families with kids and the college age set (or those about-to-be college students) who frequent the lower cost Carnival cruises.

I was in a group, but it was a group's sake for dinner only. None of us did the same type things on board, but we all found plenty to do. I'm also not middle aged, so I can't comment from that perspective.

My advice is to plan when kids are in school. That will take away both the little kids running around (700 in Camp Carnival alone which is the young kids on my cruise) and the coeds.