We bring carabiner clips, 2 for each of us. We all carry our own backpacks and we clip a clip to each strap and clip a flip flop to each clip, so when it starts to rain, we change into the flip flops and put our sneakers & socks into the bag until the rain stops.
I bring all different color sharpies for autographs, except for the color green. For some reason that is the only color that they can not get off of the costumes.
When my kids were young & in a stroller, I would bring safety pins and a receiving blanket or towel. I would pin the blanket to the shade of the stroller. When the baby/child fell asleep, I would put the shade up and pull the blanket down over the bar/table to keep the sun out. While they were sleeping I would clip a fan to the stroller and have it blowing on them while they slept. It worked perfectly.
If you are planning on getting a henna tattoo, bring a small jar of Vasoline because you need to put the Vasoline on the tattoo while you are showering or swimming, it's not supposed to get wet. When we did it, I couldn't find any Vasoline on property to buy, so I ended up using triple antibiotic ointment cause it was gel-like.