I would do 12:00 if you're being conservative.
The reality is that the ship could be late, there could be traffic, there could be a storm, there could be 1,000 different things that could go wrong. However, the most likely outcome is that the ship is going to dock on time, you can skip breakfast in the MDR, you can even just skip breakfast and get off as soon as they allow it. The most likely outcome is that you can get to the airport very early and then be bored out of your mind. And especially if you have kids...oh my god.