I've managed to grab an Anna & Elsa FP+ for my daughter 4 hours before our flight leaves MCO.
Congratulations. You are smart to know that it will take some planning.
See Anna & Elsa with FP+: 1hr
Monorail to Polynesian & get in rental car: 30 mins
Drive to airport: 45 mins
Drop off car and go through security: 45 mins
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TOTAL time spent: 2hr 45 min
Remaining time before takeoff: 50 mins
As already noted in this thread, those numbers don't quite add up. But the basic plan is sound -- if you do everything you can to avoid delays of 15 minutes here and there, which can add up quickly.
A few thoughts:
Although it's worth reading all the ideas and advice in this thread, I think some of the ideas are better than others.
When you rent your car, make sure you get a car with a real trunk, not a hatchback, minivan, or SUV.
Unless you use Resort Airline Check-in (RAC), you'll have to allow for time at your airline's counter at the airport (or with a skycap at the airport). So use RAC by all means.
You are staying at the Poly. Before going to the MK, vacate your room so that you won't have to stop at your room before driving to the airport. Hide your carry-on and personal items in the trunk. Move your car to the end of the Poly parking lot closest to the TTC.
Figure out a "must leave" time for the MK and an exit strategy for the Anna & Elsa line. If, despite your FastPass+, you find yourself waiting for too long, be prepared to leave before reaching Anna & Elsa.
After leaving the MK, plan on taking the Express Monorail to the TTC. But if there is a line that will prevent you from being on the next monorail, head to the ferry instead.
[I understand the logic behind the idea of using valet parking at the Contemporary, but by the time you walk to the Contemporary and wait for your car to be retrieved, it's unlikely that you will really save any time compared to heading to the Poly parking lot via the TTC, and you'll pay the valet parking fee and a tip. It also takes a few minutes longer to drive from the Contemporary than from the Poly, erasing more of any time you might have saved.]
Take 417 to the airport, not I-4 and 528. Traffic slowdowns on 417 are rare (unless there's a serious accident), while the slightly shorter I-4+528 route can have serious traffic slowdowns, especially on the I-4 segment, just because of heavy use.
You can return your rental car without stopping for gas if you find yourself running behind schedule. You'll pay more to the rental company, but you can make up some valuable time.
The advice to "skip the long security line using TSA pre-check" only works if you make arrangements well ahead of time and pay for the service. Even then, I've been at MCO when TSA pre-check has been closed and I had to wait in the regular line. And I've been "randomly selected" for extra screening, even when using TSA pre-check.
Remember that flights normally begin boarding 30 minutes before scheduled departure.
