I have learned after attending many retreats that less is far easier. My Bernina in its travel bag is heavy enough. I try to pre cut what I can and put all fabric into a large ziplock. If it's a workshop I only bring that class's fabric, if it's a retreat I bring two projects. Gear wise I can fit my smaller cutting mat, my rotary and my 12.5" ruler in a tote with my zip locked project. I have a pencil case that I always keep my smaller bits in (scissors, stitch ripper, spare piecing thread, hand needles, etc.) and it's easy to pop that into the tote.
If it's a four day retreat I pack some wips, and a brand new project in a Rubbermaid tote and leave it in the car. If I need it or one of the projects it's easy to grab.