Without reading all the previous posts, I'll mention what I take to my twice yearly retreats.
I purchased an inexpensive wire shopping cart (the ones with 2 wheels). I can fit most all I need into it.
Then I don't have to carry it all!
I cut a plywood board the size of a wooden TV tray, cover it with batting and some old fabric, staple.
Viola, ironing surface. Your retreat organizers should have full size ironing boards. Ours also provides full size cutting mats too.
I always take my back support that slides over the back of a chair.
I try to cut all the fabric I can for my projects ahead of time.
Have a great time!