Many good ideas here. I go on a quilt retreat every month for 4-5 days. The local retreat center has a yearly pass which I have asked for as my Christmas gift for the last 4-5 yrs. Make sure you pack ALL your machine cords, and an extension cord (if you don't know the set up) & specialty feet. I always try to cut at home as cutting tables are usually minimal in number. Some retreats allow individual irons, some don't depending on fire codes and wattage limits.
I never get as much done as I hope, but bring several projects in case you get tired of one or hit a snag. But most of all............go to relax, visit and have fun. I learn a lot from others and you get so many ideas and tips along the way. I bring my own pillow as I am a pillow snob, a nightlight or flashlight in case I have to get up in the middle of the night LOL, a humidifier in the winter as the air is sooooooooo dry and don't forget to pack your suitcase, pills and toiletries. I have been at retreats where they were so busy gathering their sewing supplies, they forgot their clothes, or their underwear, and had to rush to the nearest Wallie World.