We have done MK on party day more than once (actually did it twice for MNSSP last year). For
MVMCP we stay in the park the entire day. For
MNSSHP, we usually run back to the resort in the afternoon for a quick change into costumes as we don't want to have to bring them and carry them around or rent a locker. That is the only hassle about MNSSHP, is that it does take time out of our day to go change. As far as the party credentials, starting at 4 (and sometimes a little earlier), there will be places set up where you can go inside the park to get your wristband. There is usually one in Tomorrowland, and last year I think they also had one in Fantasyland because I think we got our tickets there. You can also go back to the front of the park and get the wristband there. As you are using a ticket for MK that day, a tip if you do leave the park and the Halloween party line is long to get into the park--- just go through the regular shorter line and then go get your wristband somewhere else. That is what we did last year one day when we got back from changing into costume.
If meeting Jack and Sally is a priority and you want to be near the front of the line, I would say to have someone in line by 4:30 (maybe 4:25, to beat everyone else that shows up at 4:30). Last year, they were coming out by 6, and sometimes at 5:30 or even sometimes as early as 5- and guests just had to show their wristband to get in line. The year before they were coming out at 6:15. The word spread that they were getting out early over the last 2 years, which means the line has built pretty early I think. If you aren't going to one of the first parties, I would keep an eye on the Dis and see if they are coming out early this year. 2 years ago-we got in line at 5:30, and it was packed by 5:45- that was when they had just started coming out early. We were probably about 9 families back. They came out at 6:00 and we were done by 6:10. Last year when we got there around 5:30, they were already out and we were significantly farther back in line. It still was fine though because with them coming out at 6, we were still done before the official 7:00 p.m. party start, but I think we waited about 45 minutes to an hour in line. We went to 3 parties last year (only waited in line for them once), and one party their line was 2 hours long right at 7 even though they had been out since at least 6:00 p.m. If the Dwarves are of interest, if you can get yourself in the front of the Jack and Sally line and they come out by 5:30 or so, then you can still probably get to the Dwarves line before it builds up too much. Last year, we got to that one just before 6:00 (different party night than Jack and Sally), and it wasn't horrible yet. They came out about 6:45 that night, and we were done not too long after the party started. Last year, an awful line was the one where they had Daisy, Donald, and Minnie all set up in the same line instead of splitting them apart like in past years. We had never waited more than 10 minutes for any of them. Last year, with it being one line, we were told it would be 40 minutes when we got in it, but it wound up taking an hour and 20 minutes! That was the longest line we waited in for anyone. I don't know if they will have one line for them again this year because I heard lots of people complaining about that last year.
