Place the child on one of the horses of the carousel and give it the magnet. Don’t turn on the carousel just yet. Stand in the middle of the carousel with the magnetometer. You are now measuring the spin dipole distribution. Take the magnet away from the child and give it the electrically charged ball (and maybe some rubber gloves to hold it). Stand again in the center with your magnetometer and turn the carousel on. The charged ball will create a current loop and thus a magnetic field. This is the orbital contribution. Now for the Fermi contact term, I’m not sure. Maybe let the child run randomly back and forth along the radius of the carousel? Although I don’t see how that would incorporate this effect of spin up/down asymmetry… Maybe it can’t be explained in such a vulgarised way?