Hi Gladys,
Thank you so much for coming to planDisney with your question. I am happy to help you think about how to plan your trip to Walt Disney World!
It sounds like you have your
theme park tickets all set up with the
Park Hopper Option, which is great. The Park Hopper Option will allow you to visit more than one theme park per day. Park Hopping hours generally start at 2:00 p.m., which means that this is the time at which you can enter a second theme park for the day.
Mickey's Not-So-Scary Halloween Party is a separately ticketed event. This means that on those party nights, guests must have a separately purchased ticket to attend Mickey's Not-So-Scary Halloween Party to be in the Magic Kingdom after 7:00 p.m., which is when this event starts. On nights that Mickey's No-So-Scary Halloween Party is taking place, Magic Kingdom typically closes for regularly ticketed theme park guests at 6:00 p.m. If you do not have a Mickey's Not-So-Scary Halloween Party ticket, you will not be able to remain in the Magic Kingdom on a night when it is taking place.
You do have a couple of options. You could Park Hop to
Magic Kingdom on an afternoon when there is a Mickey's Not-So-Scary Halloween Party planned; however, you would need to exit the park before the party begins, so you would have limited hours at the Magic Kingdom. Since you mention that you want to visit Magic Kingdom at night, this is probably not the best option for you as you would have to leave Magic Kingdom before nightfall.
I would suggest if possible that you choose a day that does not have a Mickey's Not-So-Scary Halloween Party planned to head to Magic Kingdom. Once you have Park Hopped, you are welcome to stay at Magic Kingdom until park closing, which on non-party nights will be much later. From the Magic Kingdom link I provided, you can click on "park hours" to check what the hours are each night.
I hope that this information is helpful for you, Gladys! Please feel free to come on back to planDisney if we can help you further with your Walt Disney World planning!
~ Mona Leigh