When scanning a drawing into your computer it will always load as a bitmap image, (a bit like a photograph in a newspaper). This can be sent directly to a stamp manufacturer as long as it is a black and white scan and the line thicknesses do not fall below the minimum. If the lines are too thin you can convert the bitmap image into vector data by applying a trace to the image. Programs that have tracing ability place a vector line around the lines or can be set to follow the lines, these lines can then have a thickness applied to make them suitable for rubber stamp making.
Once you've found a usable image, print yourself a copy of any images with labeled parts. Then use a paint program to white out the labels and print that copy for your child. Your child can label or color the image and have both art and science lesson at the same time.
Clip art used to be clipped from one medium and stuck to another as part of layout design. This clipart caught on quick and spread faster than a Greek army inside the walls of Troy. Free clipart became the new epidemic, infecting designers high and low with its accessibility, utility, and quirkiness.