5k and 10k days should be fine. Saturday the 12th is the half marathon day, and that one could be problematic. The race should finish about 10am, and the course is usually from Epcot to Magic Kingdom and back. Buses that cross the race route will be slow due to detours, and that may affect the whole system. If you've got a morning flight, take that into account. If you're in Epcot, there will be special crossings to get across the race route, but they shouldn't be a major problem that early.
Once the race is done (call it 9:30 or so to get off the main roads, 10 to get off of the Epcot entrance ramp, and 10:15 to get out of Epcot) things should go back to normal pretty quickly. Disney's got a lot of practice in cleaning things up after the race.
It looks like you'll be gone before the marathon on Sunday, but for anyone else looking for info - the race goes until about 1pm and touches all four parks, so the effects are broader and last longer. The crossing points are in Animal Kingdom, Studios, and Epcot, and you can end up with a 15-30 minute line just to get across the race route. If you can avoid the roads, I recommend it - boats are good, walking distance to parks is better. Monorail is apparently a mess, unfortunately. (Never stayed in a monorail resort, so that's news to me.)