I think the first seating of the Ohana character breakfast is 7:30 or something. You could wake up early, have a character breakfast, drive to the port and still be among the first in line.
Unless you are a handicapped passenger in a suite, you won't be the first to board no matter what time you arrive. They board handicapped people and suite passengers (who are at the terminal, granted some suite passengers and handicapped passengers don't arrive until later) first. So once you make the determination to be one of the first 50 or so people on board, it stops making such a big difference if you are there at 10am or 10:45.