Where to place RF shield
If your worried about the pump PWM generating frequencies in the 2.4GHz range then short the currents out on the board by using low impedance caps (low ESR and ESL).



X2Y caps are a good option, they have a lower impedance than regular caps because they have two terminals that halves the ESL. Lower ESL means higher performance at high frequencies. 


Source: https://www.farnell.com/datasheets/2046090.pdf