It depends on your day. Friday is the 5k, which last year ran around World Showcase, and they should be done by 8 am. Saturday is the 10k, which affects Epcot and the Epcot resorts, including Sea Breeze Point. However, it should be done by 9 am, and if your ceremony is in the late morning or afterwards, you shouldn't have a problem. However, on both days, you would not be able to have an Epcot bridal portrait.
Sunday is the half marathon, which will affect Epcot, Magic Kingdom, and World Drive, which connects the two. You will not be able to have a Magic Kingdom Portrait session, but you could have an Epcot bridal portrait because the race does not run through World Showcase. It also does not affect the Epcot Resorts, so Sea Breeze Point is open. We were told that they would not allow any weddings during Princess Half at the Wedding Pavilion because the race makes transportation very difficult, and DFTW had a hard time keeping things on time as a result. However, the afternoon or evening could be possible. The race should be done by 11 am at the latest.
If your ceremony is at Sea Breeze Point on Sunday, you might have transportation issues if your room block has any Magic Kingdom resorts because World Drive will be blocked off. However, you should be fine if you're in the afternoon, and since your
Pixar Place reception can't occur until after DHS closes that night, it won't be an issue.