Your question has two sides: Will it be a get-together, something that is informal and upbeat, or will it be a stiff and maybe boring meeting?
Personally, I would plan for and choose to attend a cheery get-together at a nice but informal restaurant like a great buffet (all-you-can-eat) which should please everyone. Ask in advance, have each affiliate respond, make a reservation. Use the time during dinner to know each other and just have fun.
During i.e. coffee after dinner you can discuss SFI. Go around the table and allow each person one minute (based on a group of 12) to talk about anything SFI. Allow maybe another 15-20 minutes (30 if they won't throw you out of the restaurant) for discussion.
In the end all of you should have your stomachs full and your hearts and minds fed, too.
Your question has two sides: Will it be a get-together, something that is informal and upbeat, or will it be a stiff and maybe boring meeting?
Personally, I would plan for and choose to attend a cheery get-together at a nice but informal restaurant like a great buffet (all-you-can-eat) which should please everyone. Ask in advance, have each affiliate respond, make a reservation. Use the time during dinner to know each other and just have fun.