Place the magentometer at the center of the carousel. If the child holds the magnet and the carousel is not turning yet, the magnet creates a magnetic dipole field. This is already one hyperfine field.

If the child holds the electrically charged ball and the carousel is turning, a current loop around the magnetometer is created, resulting in an orbital magnetic field, a second hyperfine field.

If the magnet and the ball are at the same place on the carousel and the carousel is turning, i think you can measure a magnetic dipole and magnetic orbital field in the magnetometer at the same time.

Maybe you can also measure a magnetic fermi field if the child is running towards the center and back again towards the edge of the carousel, representing the wavefunction of the ball, but I’m not sure if this is correct.