I arrive at roughly 330PM at the Orlando Airport. We have set up Epcot Fast Passes for 6pm, 7pm, and 8pm. How often do Magical Express buses depart the Airport? Will we have to wait hours for arrival of other guests at the airport as a shared service?”

Hi Logan! Thanks for bringing your great planning question to the Disney Parks Moms Panel! This question shows that you are a very good Walt Disney World Resort vacation planner. I can really appreciate that you are trying to maximize every moment of the magic!
 
Not knowing which resort you have booked makes this question slightly more challenging, but I'll give you my best advice based upon past experience. You are going to be absolutely fine with your 7:00PM and 8:00PM FastPass reservations. I am not nearly as comfortable with your 6:00PM reservation. I tried doing exactly what you are planning and it ended up stressing out the family upon our arrival. It wasn't a good start to our vacation and I made it a point to never book a reservation so close to arrival again.

While Disney's Magical Express is a great perk (and not too long of a wait) you can't plan on an immediate departure from Orlando International to your resort. They will wait to fill that bus with Guests (and luggage). You then have to take into account that most Magical Express routes will drop-off Guests (and luggage) at multiple resorts (usually three). If your resort happens to be first - excellent! If your resort is last - sit back and enjoy the ride. I like seeing other resorts and actually enjoy this part of the Magical Express experience. Upon arrival to your resort, you will most likely want to access your room, use the bathroom, etc. Then you will need to get your transportation to Epcot. This will most likely mean an additional wait at your resort.

If you really want to keep that 6:00PM FastPass reservation you could consider an alternate method of transportation. The Walt Disney World Resort has Minnie Van Service available from Orlando International. Unlike the Magical Express, there is a charge for Minnie Van Service as it is operated by Lyft. This service will pick you up from Orlando International and take you directly to your resort. You will probably save enough time to make it to that 6:00PM FastPass. You can also consider a private taxi or Uber.

Logan, have a great time at Epcot (and the Walt Disney World Resort) next month! Glad to hear that you snagged FastPass reservations! Happy planning!

Hakuna Matata!  Jonathan G.