I love going to quilt retreats. I get a lot done, if I take the right projects for me. And the amount of space you'll have to yourself makes a lot of difference. I get easily distracted. So I take something I don't need to concentrate on. What I've found works best for me, is quilting the sandwich. I don't need a lot of supplies, so it's easy to pack. People have told me they like to watch me put a design together (I do art quilts with no planned direction). Occassionally, when I know the classroom specifics, I'll take an art project in very predefined fabrics. This requires a design board, small cutting board and Clover mini wand iron with pressing mat. Plenty of table space, a lot of supplies and plenty of classroom space. So this is a luxury.
I'd agree with keeping cutting at the retreat to a minimum. Cut it out at home.
And take several projects. Make a list and pack several days in advance so you have time to remember other things you want to bring. At every retreat, people have been willing to share if you forget something.
Take a task light, a cushion for your chair, power strip with plenty of cord. Dress in layers. If you're usually hot-a fan; if cold, sit to the center of the room and take a warm layer. Oh yes, wheels. No matter how close you can park, toting heavy supplies is tiresome.
At one retreat I had one side of a 4' table and even less space behind me. It was very hard to move. That got corrected the next retreat. The retreat had grown in popularity so quickly and the people setting up didn't know what to do with all of us. It's still one of my favorite retreats.
Take what makes you happy, talk with the organizer to see what they provide, and be flexible.