Great advice above. I keep a list in one of my sewing bags, so I know what I want to take each time. I take a long corded surge protector for my machine as I want it protected.
As for irons: some retreats supply the irons and request you not bring any with you to prevent power outages. Irons take up a lot of power. Also, this way they can be confined to 1 or 2 areas so that is a safety issue. No chance of being accidentlly burned by your quilting neighbor's iron.
I also take at least 1 plastic cup with a closing type lid for my coffee/water/tea. I surely wouldn't appreciate it if someone's coffee spilled onto my work, so I honor others this way. I also honor my own work this way.