Hi Jacalyn!
If you have never experienced the great
Mickey's Not So Scary Halloween Party in the Magic Kingdom you are in for a real treat. It will certainly get you into the spooky holiday spirit. The party dates certainly surprised us with such an early start but that will make so many more guests happy that they can experience it.
I strongly suggest the family choose a costume or hats or shirts that bring them together for the festivities as a group. It is so much fun to see the pictures when you are all dressed up and have a theme. Just remember that in August the weather will still be quite hot and humid and still a good chance of rain so keep that in mind when thinking about what you want to wear. Disney does not allow masks so just choose something simply yet fun and in good taste. And don't forget to decorate the ECV!
Your event ticket will allow you entrance to the park as early as 4pm. The party does not officially begin until 7pm but this gives you a chance to dine or enjoy a couple of attractions before the start time. Some guests enjoy doing some character meet and greets or enjoy some things that you often would not stop to see such as the flag retreat in front of the train station.
Once 7pm hits you will want to head for the fun trick or treat spots and start enjoying the shorter lines for the rides and shows. Most of the attractions are open during the party and if you have little dancers int he group there is a DJ in Tomorrowland playing some lively tunes.
There will be two parades and my suggestion is to wait for the second one when the crowds thin out. Make sure you find a spot early enough as the Headless Horseman makes a run through the park about 20 minutes before. Definitely also stay for the fireworks and castle show which are special for this party and try to stay to the end!