We took a group of 24 two years ago, it started as a 'group getaway' but several months into the planning I was told that they no longer do the 'groups'. They did link all the ressies (we supplied DVC rooms for everyone) and they were all supposed to be close together. Several were fairly close, sadly our son & family and daughter & family were on a different floor quite a jaunt from us.
We did arrange a welcome dinner for everyone at Sanaa, going through Sanaa management to arrange it. We also went through Disney events/catering and rented an overlook in Epcot and had appetizers, drinks, etc....that was marvelous but pricey. We were celebrating our 40th anniversary so we wanted special times for all to remember.
I sent out newsletters (email) to help those who weren't familiar with WDW with facts about the buses, the hours, Magical Express, etc.
We loved it and will probably do it again at 45 years.