Congratulations!
We attended an Epcot MM a few years ago.
First off - if they give you a food voucher - use that before the park closes (i.e., if they give you early entry at 6pm, go eat then). Be prepared to wait a while for your food - you won't be the only ones with that idea. Most food options close with the park. Back when we went, all merchandise and food locations in world showcase closed at park close so it was just future world rides open. They did have t-shirts you could buy, a dance party, rides, free "snacks" (ice cream and popcorn I think?), and special fireworks.
DVC senior staff was there for a meet and greet, and there was special character experiences. The fireworks show was AWESOME.
Went to Soarin right after park close and rode all by ourselves. literally. It was only our party in the entire theater.
I hope you have a great time!