Because so much is at stake, I would encourage youth ministers to do whatever it takes to get a good percentage of each of those groups to the meeting. It is worth writing personal notes. It is worth visits to homes. It is worth spending Sunday afternoon on the phone. It is worth whatever it takes.
Attendance is a key variable, but the content of the meeting is also.
The appearance of the meeting room should suggest something important is about to happen. Any handouts should be well-developed. Most importantly, the youth minister's presentation should be carefully prepared. This is no time to wing it. I suggest this outline, modified to fit each church's unique situation.