Howdy, Matthew!
Welcome back to the Disney Parks Moms Panel!
Mickey's Backyard BBQ is a knew-slapping good time with Mickey and gang. This dinner show is also a great way to experience some of the routin'-tootin' magical fun available outside of the theme parks.
This hoedown is held on select nights in the open-air Fort Wilderness Pavillon, located not far from the boat launch and right behind Pioneer Hall - due to its location, you're definitely better off taking the ferry from Magic Kingdom to Disney's Fort Wilderness Resort and Campground! If you drive from Magic Kingdom, you'll have to take the Monorail to the Transportation and Ticket Center, a Tram back to your car, and then an Internal Shuttle from the front entrance/parking lot of Fort Wilderness to the "Settlement" bus stop.
The duration of this experience is 90 minutes in length, so you can expect for it to conclude around 8pm. However, official park hours for your travel dates are still a few weeks away from being released. As long as that night's showing of Happily Ever After is scheduled for 9pm or later, with a little Faith, Trust, and Pixie Dust, I do believe you'll make it back in time. You might not have the viewing location you had hoped for, but you should be back at Magic Kingdom right at 9pm. Taking the boat launch back will be the fastest route. Keep in mind, Hoop-Dee-Doo Musical Revue will have also let out, so lines may be long.
I hope this is helpful in your planning, Matthew! Keep an eye on the
park hours calendar and please let me know if you should have any additional questions.
Faith