Dinner/Dance like the 20th (use a professional reunion company)
Casual adults-only BBQ event (need LOTS of people willing to help in small ways!)
Choose a nice hotel, get a bunch of rooms, hang out at the pool, bar, etc. Everyone pays for their own stuff, everything is informal.
Find a restaurant/club that will let us take over the place for the evening. Everyone pays for their own food/drinks.
Let's not have a reunion...wait for the 30th.