Bad analogy regarding the airline vs cruise line. The flight is already in progress. To be correct, I would have to be on the cruise and expect butler service in my standard cabin (assuming Carnival had butlers). Of course I wouldn't!
A more correct analogy would be if I bought my wife a 1st class airline ticket and I had a coach seat. We go to the airport to check-in and they forced us to split up, with her going to the special 1st class check-in line. In this case, I would still go with her to the 1st class line. In fact, I have done this in a business climate where one guy had enough miles for an upgrade. The airline didn't care.
I guess I should have been clearer in my original post. I am talking about 4 people for the cruise - all one family. Me in the standard cabin, my wife, her mom, and my son in the suite. I am using the standard cabin as an extra bedroom (I snore).