I have also made cool ties......I don't know what the weather is like where they are going, but these would be good in the hot weather - you soak these in cold water and the water gems swell up 6 times their original size with the water, then you wear it around your head or neck to keep cool.
Here is how I constructed them: Water Gems are generally used for flower arrangements or as a soil hydrator for plants. Do not put these down your drains.....
Cut 45 inches on the bias of your fabric, tapering each end, now with right sides together, stitch approx, 15 inches from each end, leaving an opening an opening of approx 15 inches to place your water gems into. Fold over the edges and stitch down this opening. and you are done.
For those of you that cannot find water gems, baby diapers also have a water retention and liner with these water beads, to keep the child dry, your need to be careful with these, as they are very fine, try to keep them inside their liner, and insert the liner and beads inside the opening of the tie - these granules are very fine, but work the same as the water beads, you can probably get a couple of inserts from one new diaper.