freehand sketch or drawing to g code

[Sven]

You can do it using inkscape to convert the scan to a dxf (takes a few steps) and then use f-engrave to turn it in to gcode.
These programs are open source and free to use.

As mentioned above, Inkscape by itself might also work, but a plugin woukld be needed, one that I have not been able to get working.

But all of this would be hard to explain to someone who is not that in to computers....