You might contact a quilting store or Joann's, since it is for 4-H they may donate some end pieces or sale fabric, as for rulers, cutters and other supplies the kids themselves might know someone that quilts that has extra or old cutting mats that can be used on the back side. Teach them how to make their own templets from something recycled is a way to save money. Learning thrift at an early age is a life lesson.
I think you have a fantastic idea.