The half marathon is January 9 and the full marathon is January 10. I know because I crazily signed up to run both this year. I'm doing my trip after the races as I think it will be a little less crowded that week then the week leading up to it. However, if I wasn't running then I'd probably do the trip another week later just to be safe from the crowds. That being said, this is my first time both running in the WDW marathon and taking a January trip to WDW.
Thanks for the info