Question for the marathon vets:
Has anyone ever done all four parks after the marathon? Is it doable or really a crazy idea?
I'm not planning on doing anything super intense - right now I'm thinking Mickey M&G (possibly also Minnie, since she will be my marathon costume), Starbucks, and one attraction in each park, so it won't be too crazy, but I just don't know if even that is getting myself in over my head.
I've done more than one park after the marathon but we haven't ever done all 4. I think the biggest issue you'll have is lines and transit times. Ariel and others have some pretty good points. A lot of this will depend on the transit situation, your finish time and if you want to go back to the room post race.
Best case scenario. (fast marathon with car)
Start Marathon at 5:45 and finish by 9:45 (Four hour Marathon Pace)
By the time you exit the Finish are and have eaten something potentially freshened up a bit it will be 10:15.
By the time you walk to your car, stow your stuff then walk to the front of the park, and go through security and the turnstiles it will be 10:45 ish
I am guessing that you could do an attraction, Sbucks and the pic in Epcot in 1:30 minutes.
Leave Epcot at 12:15 and drive to Studios.
The parks will be more crowded there so I think you'll probably need closer to 2 hours to do everything there including getting in through security.
That would set you up to leave Studios at 2:30
Leave Studios at 2:30 and get to AK by 2:50
I would budget more time for AK so that you could stop either at Nomad Lounge, Satuli, or Flame Tree for some real food.
I think you could do what you want at AK and be on the way out by 6:30
Head from there to MK. I'm guessing it could take upwards of an hour to get from AK to the front of MK.
If you arrive there by 7:30 it should give you time to do everything you want.
If your marathon is slower parks, will be more crowded and my guess is that the time getting into the parks and the time spent in each park would be longer too. I also know that, that would be a lot of walking. It also doesn't really give you time to get cleaned up post race. I think it is possible, but it might not be very fun.