We went to MNSSHP 1st party 9/2/2016 and I will say everything is going to be crowded and take much longer than your time frames allow.
For instance if you arrive MK at 4:00 there will long lines to get into park at that time.
You should return to MK no later than 3:00 and then get in a short line inside the park to get your wrist band at 4.
If one line looks too long than just keep walking until you find a shorter line, no one will be able to tell you where the lines are you just have to find one.
Make sure to get a special MNNSHP map.
They won't hand you one but there right in the area of the wrist bands.
The special map is important it will have the parade and show schedules and places to meet the characters~ important since times and places for M&G are not always the same from year to year.
Same goes for a treat bag they don't' hand them out you just have to search the area for them. Even if you don't think you want candy it's fun to get some and the bags are gone quickly.
Also you will want to check on when to line up for Minnie Daisy and Donald, the year we were there people were line up well before those characters arrived.
We came across Lotso and the line was very short compared to the other lines and that took 1/2 hour to get through.
Most ride lines are not bad.
We picked up our wrists band outside Pirates of Caribbean and line was 15min so we hopped into that line.
Haunted Mansion for Halloween festivities is a lot of fun we had a 6-6:30 fast pass for that to ensure we wouldn't waste too much of our party time in line.
Afterward we took our photos with Madame Carlotta who was standing outside the exit as we left Haunted Mansion.
It was just me and my daughter and we found space easily 15 minutes before shows and 20 min before parades. We sat over near the stockade for the parade.
We did everything we wanted but I had a strict time line.
Be organized because the evening is a whirl and over before you get your bearings.
It all felt a bit overwhelming, especially the beginning of the event.
I was surprised how uninformed the CM were ~they kept saying its the first party and we weren't given any information either sorry we can't help you.
I "dressed-up" for the event, to my teen daughters chagrin.
I wore a Jack Skellington tuxedo t-shirt and Jack and Sally Mickey ears.
I was so upset I forgot my Jack long skinny finger gloves back at the hotel to my daughters delight

Many people were dressed in costume for the occasion.
It is so much fun ~you will enjoy yourselves.