This is very similar to running a theatrical production. I used to direct shows and had to deal with a lot of egos. What I found works pretty well is to explain about the "not a democracy" part right off the bat and make it very clear that while you respect everyone's opinions and ideas, no one is to interrupt while we are putting together a show. I would say something like, "If you have ideas, I would love to hear them later and may well use them but not in the middle of this well planned procedure." On a sailboat or in a show there cannot be more than one person in charge. It leads to chaos and very possibly, danger on a deck or a stage.
Alberg 35: With a philosophical flourish Cato throws himself upon his sword; I quietly take to the ship.