Another option I just recently became aware of for Philly area flyers is to fly Allegiant Air from Lehigh Valley International in Allentown (ABE) to Sanford-Orlando Airport (SFB).
I just recently found out about them, and it looks like a very nice alternative.
ABE airport is about 20 minutes further from Chester Springs than PHL is, but the airport itself is much smaller so total time from door to gate is probably about the same.
Similarly at Sanford, the airport is 20-30 minutes further from Disney, but is much smaller than MCO.
It looks like their typical non-peak fare is $79 each way, and the website offers air/car rental discount packages.
I was able to find round trip for 4 with minivan car rental from
Alamo for a week for under $1000 total from their website.
If we weren't going on the Autotrain as part of the vacation travel adventure this time, I would definitely consider canceling that reservation and changing to Allegiant.
The only drawback is that they only have 1 flight per day each direction - and it looks like they are in the evening (6-ish departure, 9-ish arrival each way). That means an extra hotel night in Orlando, but it also means that departure day can be a park day as well!
Ted