It depends. What day of the week are you getting it, and how long are you keeping it? Many special rates are restricted to certain days and times, and if you have one of those you will not be allowed to pick it up very early without getting reassessed at whatever current rate is available.
(No more than an hour early is usually fine, though; unless you got a weekend rate, in which case no time earlier than noon on Thursday will let you keep it.)
I would suggest that if all else fails, be prepared to kill 5 hours in the airport &/or the onsite Marriott. If you are staying onsite, you could book most of the party on ME, and have only one person wait around for the car rental. (I'd suggest going to your resort and coming back for it, but IME with car rentals at MCO during the pandemic, they are REALLLLLLY slow, so I don't think that would work well. Unless it has changed in the past month or so, all rentals have to go to the counter right now, and they also tend to be short-staffed. The 3 times we have been since last April, it took me nearly 2 hours to get the car rental processed due to the length of the line.)