I went to the park on October 2nd at 3:30pm. At 4:00pm they handed out bracelets in a bunch of locations in the park. My family just went on a bunch of attractions until the party started at 7:00pm. I hope that helps!
I don't remember exactly what time we got there Friday, Sept 30th but it was between 4 and 5 and we were let in with only party tickets no problem. They even had seperate lines for party tickets and regular tickets at that point.
We entered the park with just our MNSSHP tickets on Sunday at 4 pm. . . On Friday, Sept. 30, we did the same at 5 pm. We went later on Friday, because of dinner reservations.
The time between 4 and 7 on Sunday was great -- the park was getting empty, everything was a walk on. They didn't herd us to Tommorrowland as expected on Sunday between 6 and 7 -- they just let us ride whatever we wanted with our wristbands. We bounced around Splash and Big Thunder during that time. . . Almost no waiting for Peter Pan and Dumbo, too.