But Gas, that's how things get done. All you need to do is have a few more meetings. See, what happens is that first you need a meeting to discuss the topic or topics that need to be discussed in your upcoming meeting. Then you can have a meeting to discuss who should be invited to the meeting discussing the topics brought up in the previous meeting. And then, because some of the people who are going to be invited hadn't been at the first meeting, you need to hold that original topic setting meeting again, in case the new attendees have something to contribute (because why else would you invite them, right?). Then, because the topics have changed, you need to re-evaluate who should be invited to the meeting to discuss the topics that you've discussed discussing. Only when you are absolutely certain that you have everyone that you need and all of the topics are laid out, you need to have a meeting to lay out the specific agenda for the upcoming meeting, as well as to schedule when that meeting will be held.
Now, it's only natural for a few topics to have been left off the agenda, because they weren't deemed important enough to take time discussing with everyone that's going to be attending, or because some attendees couldn't attend at the given time and date; so you'll need to reschedule a meeting to put together an agenda for the topics that were left off the original agenda, and have the requisite meetings to discuss who to invite to that meeting, and when to schedule it. By this time, hopefully, you've had the meeting to discuss the original agenda. If so, you probably spent more time talking to the attendees of the meeting about why you were having this meeting, and didn't really discuss everything that you needed to discuss during the meeting. One great strategy for how to deal with this is to add all of the people that were going to be coming to the second meeting to a follow-up meeting for the first meeting, so you can just get everything back on one agenda. However, you also need to remember that none of the people that were going to be at the second agenda meeting were at the first agenda meeting, so you'll need to make sure you go back over the presentation about why you've called a meeting to discuss the items on the agenda. Then, once all of that is done, you can have a meeting to discuss the agenda. Finally, when the last group meeting is done, each individual department involved in the meetings should go off and have their own meetings to decide what to actually do.
Along the way, you should be sure to yell, scream, throw things, break furniture, slam doors, and demean all of your employees for not getting stuff done, because that's what you're having all of these meetings about, god damn it!