The Food & Wine Fest race is actually a half marathon. It runs at night, started at 10PM last year, and went through AK, DHS, and finished at Epcot. They have changed the course a bit this year, but haven't released the official course map. Since it takes place at night (and starts at the WWoS), the race itself won't affect the parks at all.
This event only had about 12000 runners last year, I would imagine they will cap it at like 15,000 or so this year. Will it really affect the crowds? I think the bigger problem you will run into is that it is the opening weekend for F&W fest. (At least it was this past year) There will be a slight crowd bump from the runners, but I have found that a large chunk of them just make it a long weekend (From doing 4 of the non January Marathon weekend race weekends). And as part of that, they have a chunk of time to register/visit the expo.
Due to the late start time, I believe the runners need to be on the buses by about 7PM Saturday or so (factor in prep time beforehand as well), and most will sleep in Sunday due to the late night (most people won't even finish til after midnight, never mind the post race party in Epcot), it should help to keep the crowds down in the parks. You will have a bump at on site hotels, especially the ones that are host resorts. If you aren't staying at a host resort, you probably won't see that much from the half marathon weekend except for the people wearing their event shirts and possibly their medals.
