Let's see math wise last corral starts at 630/640 and ttc parking lot is miles 3/4 so I'd say road clear wouldn't be before 730ish at the earliest so To me ttc is a bad idea esp if it's only to avoid the parking fee.. (Which unless you were going around the 'back' which would be closed since it's the back half of the course you'd prob have to pay the fee anyway cause they'd be in 'breakfast mode' about then anyway with a 9 am open)
honestly I'd realize time= money, aim for semi closer to your expected finish (say 815/830) and pay the parking fee knowing they are right where they need to be with less time to entertain the kids.. Plus itd be good all day if you were planning park time later...
I'd hate for them to have parking issues, monorail issues etc and miss you finish..