Given the lack of coverage that many bikinis offer these days, I doubt that having a topless deck is a big reason to label Carnival as not being family friendly. The biggest show I have seen on a cruise was with Princess a few years ago when one girl lounged in a bathing suit of mostly strings - and this was at the main pools. She showed more than anyone on a Carnival topless deck would.
We have had our cruise booked for several months and I just heard a few weeks ago about the topless deck. I just think parents should know that it is there! As a parent of a teenage boy, I'm not for sure there will be a way to keep him away from there, I just wish that when you choose a "family vacation", these things would be made known!!! Can't protect them forever, but yet don't want to send a negative message to our kids either!!! Oh well, I am planning to have a wonderful vacation!!