What you are bringing sounds good.
When my guild has its 2 day retreats, I also like to have:
Tools: machine oil and cleaning brush, an extra blade, extra camera batteries. Be sure you have bobbins and thread for your projects.
Are you planning to do binding? Will you need hand sewing needles?
I like a cushion for my tush because our chairs are very hard.
Food? Drink? We generally brings snacks as well as have a pot luck towards the end. Be sure you have whatever you like to drink. Where we meet, we need to bring plates, cups, utensils as well.