Hiya Zakeira! Welcome to planDisney!
Oh boy! I'm excited you'll be attending
Mickey's Not So Scary Halloween Party in just a few weeks! This is my favorite event of the year, mostly because it mixes my love of Disney Parks with such a fun holiday!
Entering the Magic Kingdom at 4 PM is the perfect way to get the most out of your special event ticket. You'll be able to ride attractions, grab your favorite park snack, or just take in the sights and sounds before the party officially starts. You will also have the ability to purchase
Disney Genie+ on this day. However, I would caution you on how much value you will get out of it since you'll only be able to utilize it from 4 PM to 6 PM. Genie+ will not be available during the Halloween Party.
If you purchase it in the morning before 7 AM, you can make your
first selection at this time. You will need to find an attraction that has a return time after 4 PM since you will not be able to enter before then. Since Disney Genie+ does not allow you to select the time you want to ride and only provides you with the next available time slot, you will be limited on what you can choose. If you were able to make a selection, you can then make your next choice two hours after the official park opening time. Again, make sure to select an attraction that has a time that will allow you to ride when you arrive. You can continue making selections every two hours thereafter. The major risk is not finding attractions with return windows that fit your time frame. Most likely, many of the attractions will have their next available time listed before you actually arrive.
Zakeira, I hope this information helps you plan for your stay! Have a ghoulish time during your visit!
See ya real soon!
Greg