For several years, I traveled the Sunday after Thanksgiving. A few years ago, I inquired at the resort as to the difference between coming down on Saturday and Sunday. It seemed just as good to come down on Saturday. I was told 2/3 of the people are actually checking out on Saturday, to get an extra at home with the kids before going back to school.
Here is what I found....
Saturday fares are slightly higher than normal; however much lower on Saturday, than on Sunday.
I booked very early (in April) and got an airfare of $89.00 going down and $59.00 coming back. (BTW, I checked Airtran yesterday and they are almost posting the airfare for that time period - they are very close).
I fly out of BWI at 7:00 am, so I have never hit any traffic coming to the airport. I have always been no more than fourth or fifth in the line at the Check-in for Airtran.
Parking can be an issue at the airport, because most people are not arriving back at BWI until late Saturday/all day Sunday. However, at BWI, if the extended stay parking is full, they will let you park in the garage for the same price as the extended stay lot.
When you arrive at MCO, mid-morning, it is starting to get a bit busy, but not too bad.
The wait for ME is very short, because they don't even wait to fill the buses. We arrived at the check-in, they waived us through, and put us on a bus and we maybe waited 5 minutes. The bus was not even half full. They are so busy just trying to get people back to the airport.
Once you arrive at the resort, it is fairly busy, as I arrive just as the RAC counter is winding down. Check-in takes about ten minutes or so. Now, many rooms are not ready; I have been told I can take the next available room, but I always tell them ahead of time, I would rather wait for the water view room I paid for and I don't care if it takes all day. I leave my carry-on at Guest Services and go on my way. It is around 11:00 am.
On Saturday/Sunday, avoid MK and DHS. Both very crowded with the locals. So is DTD. I arrive just as the countries are opening at Epcot, so I do the front part of Epcot. No waits, except TT and Soarin'. With the exception of Soarin', I don't need to get back to the front part of Epcot, so I do it on the first day.
Sunday, I do AK, and it is basically practically empty.
Make sure you have ADR's at least for that first weekend; many places are crowded - especially DHS, MK, and DTD - places are booked solid and say it can be up to a 1-1/2 to 2 hour wait for a table.
Hope that helps!