What I took to my retreat,
sewing machine, regular extension cord, large power supply extension, desk Ott light, bendable light, a selection of scissors and snippers, rotary cutter and an extra blade, a small cutting mat, threads for each project, pins, tape measures, fabric markers, my 4 most used rulers, extra machine needles, hand sewing needles, my favorite thimble, a small folding table, a table top ironing board, a travel iron, four projects in Art Bins and my sewing chair.
I can't recommend taking your own chair enough. A folding chair will kill your back before too long.
I never used the table top ironing board or the travel iron. I'm not taking them next time. Too many irons going in one room tends to blow breakers or fuses. Besides getting up and walking across the room once in a while is good for you.
If you're someone that gets cold you might want to take a comfy sweater or warmer shirt. Several of us had our house slippers and wore them in the sewing room instead of regular shoes.
Two of the things we needed were small bags for trash and tape to tape them to the tables. The B&B had some bags and we used a sticky roller for the tape.