Seeing the components we are given, we can let the carousel represent the atom with the center being the location of the nucleus. The electrical ball can be placed somwhere on it to represent an electron.
To find the orbital contribution, we can let the bar magnet represent the electron spin. If we then rotate the carousel and place the child with the magnetometer at the center of the carousel, they can measure the effect from the magnetic field created by a moving charge.
The dipolar contribution can be measured the same way by simply not rotating. By subtracting this contribution from the first result, we can quantify the orbital correction.
For the Fermi contribution, we bring the charged ball closer and closer to the middle of the carousel, the change we see from the dipolar case is the fermi contribution.