Hi Anne!
Thank you for bringing your question to the Disney Parks Moms Panel!
I think that the answer will depend on what time you think you will finish. If you are in an early corral and finish in four or five hours, I think parking at Epcot or riding the bus back to
Disney's Pop Century Resort would be the fastest. The bus lines and parking lots don't usually get super busy until later in the race. You will have to avoid certain roads when leaving Epcot, but it wouldn't be a huge addition of time.
If you're in a later corral and take longer than that to finish, that's when the finish area and bus lines begin getting more crowded. If that's your situation, I still think parking at Epcot would be a good idea, with parking at the
Transportation and Ticket Center as the second choice.
If you decide to park at Epcot, make sure you allow yourself plenty of time on the way to the race. That's when the traffic congestion is the worst. When I drive, I plan to get to the Epcot parking lot no later than 3:45 a.m.
I hope this helps! Please let me know if you have any other questions.