lurker's comment: I've had some get-togethers with CFC-members. Last one was in Stuttgart. I'm posting this to give you some tips.
First: decide on a location. You need someone with enough room who opens up his/her house for the guests. Without it, I think the chances of it happening are slim. Hotel cost just might tip the balance to "No" for many.
Second: decide on the date(s). Of course the host has a big say in this. My experience is that get-togethers starting of Friday-evening work out fine. The timespan is not too long nor too short and most people can make themselves available over the weekend.
Third: decide on activities you want to do / undergo. Clubbing, games, Civ in a LAN-game, chat&talk, whatever. This will give the interested people the knowledge they need to make the decision if the time + travelcost is worth it.
Fourth: Let the interested people "sign up". If there are too few, adjust the point 2 and perhaps 3. If there are too many, the host should "remove" people, or adjust points 1,2 and 3.
Fifth: make agreements about "who pays for what" and "Who brings what". Having this settled before the get-together itself prevent unnnessecary stress and irritation.
You don't need to organise travel-planning; the guests will do that themselves.
Good luck