Hi Amanda!
Thank you for bringing your question to the Disney Parks Moms Panel!
Congratulations to your husband for taking on the Dopey! It's an amazing achievement and lots of fun.
The only two days that there will be significant road closures will be Saturday and Sunday mornings, during the half marathon and full marathon. Ideally, I wouldn't plan to try to be at
Epcot either of those mornings by rope drop because that is the park and parking lot most affected. Runners will be clear of the
Magic Kingdom Park on both mornings before park opening. You could even get to the Magic Kingdom really early to see your husband run through around mile 5 (for the half and full), and then hang out outside the park until it's time for rope drop.
There will be an event guide published about two weeks before the race that will have detailed information about road closures and alternate ways to travel. It will be emailed to runners and will also be available on the
Walt Disney World Marathon website, under RUNNER INFO. Some map applications for your phone are also useful because they will know when roads are closed and re-route you automatically.
I hope this helps! Please let me know if you have any other questions.