Late flight out

We haven't finalized our return time home once the Conquest gets in on Dec. 8. If we were to seek a late flight out of New Orleans (6 p.m.), does one know if there are facilities available to store luggage? Or would we have to lug it around all day while we shop etc...before heading out to the airport to catch our flight home? I don't think you can check in at the airport more than 4 hours ahead of time. We'd really like to stay and wander around, but if we have to have our luggage with us, then we will probably go with an earlier flight. Thanks in advance

Countdown to Conquest

Carnival Victory - Nov. 2000
Carnival Spirit - Nov. 2001
Carnival Conquest - Dec. 2002