For a guaranteed viewing--he needs to be on the busses by about 5am. Once the race starts--the logjam begins and it is a royal PITA for those busses to get around.
I would suggest he hang (for the full) at the entrance to EPCOT to see you run on in--then take the monorail to MK. (Make sure you confirm with a volunteer or CM which area your color will be entering--red and blue enter at different spots).
For the half--I still suggest the 5am bus time to the start and immediate monorail over to MK.
He will never make it by bus to see you in time. I don't recall the precise moment when they close the roads---but once they do....bus transportation is a royal pain.
He will just need to suck it up and be prepared to be nearly an early bird like you!
(and by 5am, I mean no later than--a half hour or so earlier would be better.)