The best and most honorable thing to do is to change your reservation to travel that last leg to MCO and then back to LAX (assuming you are going back t o LAX). It will be a circle trip not based on two one way fares so perhaps the difference in cost won't be too much more then what you're going to pay anyway.

You may also save your wife and family some embaressment. When an agent sees that you have not boarded the flight (but flew your inbound flight) they are going to question your wife as to where you are. Whe she has to tell them you are not going they may charge you the appropriate two one way fares (LAX-CUN, CUN-ATL) If you have bags checked under your name more bells and whistles may go off.