In my limited experience many weekend warriors think they can wing most aspects of being in a band and are totally unaware of the benefits of getting more organized. I suggest discussing it at an upcoming practice. Focus on the benefits of creating and sticking to set lists and the idea that your song sequence can lead the crowd where you want it to go rather than the crowd leading you (the crowd does not know how to express that to you anyway. Including the loud drunk guy yelling for "Purple Rain" all night. Wait, that was me.) Hopefully at least some of your bandmates will support you. Above all be gentle with your request. And be prepared for it to fall on deaf ears.