I would share with the boss that I would do this in two steps. First, I would ask the leadership team to come back before the meeting with their top 3 goals for the project, and the top 3 risks they see. I would then organize everyone’s input together to report back during the meeting. In the meeting, I would reinforce where we are all aligned, and then focus on just one or two areas to discuss. That would focus the conversations (and any disagreements) and everyone would see instantly where they are already aligned.