Last time I was on Carnival, the atmosphere on deck during the day was 'frat party'; there was lots of overdrinking and innappropriate/funny behavior. It's possible to stand back and observe but total avoidance might be tough. Their food is ok, their ships decor is wild/think mixed and unco-ordinated prints, but fun for some people. They have good tours in port. Their owner is the owner of The Miami Heat-ala LeBron. He also owns Costa now. Lots and lots of people love Carnival. I prefer something a tad more sedate but that's just personal preference.
Royal Caribbean, still active but slightly more sophisticated activity would be my go to. I really love Celebrity!