Hello Patrick,
I love your plan! In fact, park-hopping at night is one of my favorite ways to end the day at Walt Disney World.
You can definitely head over to
Magic Kingdom Park after
Epcot closes. Most attractions should be operating normally and you may even get there in time to catch the fireworks, depending on show times. I suggest checking the hours using the
My Disney Experience mobile app before heading over just to make sure times haven't been changed.
There is nothing like being at Magic Kingdom after dark. The lights and sounds are so beautiful and even though many people are winding down and tired, there is a really fun energy buzzing all around.
Some of my favorite attractions to experience after dark are
Big Thunder Mountain Railroad,
Haunted Mansion, and
Astro Orbiter for a sky-high view of the park all lit up. And you'll definitely want to take a few moments to enjoy Main Street, U.S.A. and the nighttime view of Cinderella Castle.
For a quick exit from Epcot, you might want to watch
IllumiNations: Reflections of Earth from Future World. That way, you can beat some of the crowds on your way out.
Wishing you a truly magical day (and night) at Walt Disney World, Patrick. Enjoy!
Andrea U.