Hi John!
How wonderful! Walt Disney World is the perfect magical place for a wedding!
One option for a special celebration is one of the
Specialty Cruises to view Fireworks from either the Magic Kingdom or Epcot. Some cruises fit up to 10 people on a boat - so you'll need to book 2 and the Grand 1 Yacht fits 17 - which may or may not work for your group (depending on if everyone is attending).
A smaller option, which wouldn't be a private event, would be a group reservation for the
Tomorrowland Terrace Fireworks Dessert Party at the Magic Kingdom. A fun place to get together, have desserts and view Wishes, it is a more low-key event than the cruises but it still offers a great view of Wishes!
Last, but not least, group dining may be able to help you with a special, private room at a dining location. They are super helpful and have tons of experience. Give the folks at Disney Dining a call and let them know you have a large party. Their specialists should be able to help you out!
Have a wonderful and magical time!