We went this morning and The Wiggles were fabulous.
I can't answer what time the parking lot opened but when we got there around 8:05 there were only three rows of cars.
They had the end turnstile open for Wiggles guests (they just said, are you here for the show and we said yup). Then all the way back to Lights!Motors!Action! they had yellow-shirted cast members cheerfully greeting and showing the path to the tickets.
The tickets were given out in first-come-first-served order by showtime and then by "Gates" A, B, C and D. We were in the B gate group for the 9:00 show so I can't give complete specifics about all the groups or shows. One person only needed to be in this line, for each party, but that person is supposed to have everyones' admission media (tickets).
After picking up the tickets, there are more yellow shirts pointing the way to the Indiana Jones Epic Stunt Spectacular theater, where each "Gate" is well-marked and in a slightly different location.
The A group was let in at 9:30 and they were the only ones permitted in the folding-chair "floor" area (actually the stage if the Indy show was going). The B group was let in at about 9:35, and I would assume the other groups followed shortly after. Because we went straight to the theater after picking up the tickets we were second in line for the B gate and got second-row seating in the normal stands area. It was fabulous and my little ones could see perfectly.
The Wiggles came on promptly at 10:00, although without Greg. They said Greg was sick with fainting spells and had returned to Australia to see his doctor. "Sam" was Greg's replacement though I think he was only used when Greg was "necessary," such as driving in the Big Red Car. They were nice and honest about the replacement ("Sam is doing the driving ... signing scoobydoowah ..."). The show was the promised 30 minutes and they did a lot in that time!!
The yellow-shirted cast members told us that guests started arriving at 4 a.m. I slept comfortably in my bed until 7:00, so I did not begrudge their front-row-seating one little bit :=). But you COULD get in the front row of later shows out of just luck, I think, if you got an A ticket, and then were willing to wait a while for the show. We get irritated listening to a show before we get to see it so the 10:00 show was perfect for us.
I thought Disney did an awesome job of keeping everything calm, clear and fair.