It is my understanding that you can no longer book fast passes during the marathon due to the new park rules. You must scan your park ticket in order to use FPs in that park. I rode Everest during the marathon using the single rider line this year.I would be interested to know what fastpasses you were thinking of getting and how close to the tiem you have to be. I have a vague plan to try to get on one or two rides during the marathon but I've no idea of the logistics involved.
I always book my FPs for later in the day after the races so I have some buffer time.