Best advice from organising events in the past is that someone...anyone... needs to pick a date and run with it.
People may bail and some will still be up for it, but pick a date and location. Maybe best to keep it quite casual, day time park and picnic meet up. Drinks or even dinner somewhere... depending on the number dinner might be awkward due to making reservations etc...
Might also be worth setting up a group on kik or another chap application so people can join and keep in touch!
Good luck and hope you all have a fab time!
7 months