Small tent or swag. Quality is of importance. Good to have one for the kids - and one for yourselves. Pillows - small down pillows are available. They save space and pack in with the sleeping bags.
Chamois towels dry easily and take up minimal space.
Carry one big towel for swimming. Mosquito net Spare blanket if you feel the cold. Small chairs - with strength. Table if you need one. Lighting - Recharge lanterns are preferable.