I suspect you were intending to use the reed switch to implement a safety lockout, to disconnect the motors when it is nessercery to handle the robot, without having to open the presumably hermetically sealed housing.
However I have serious concerns about using a reed switch for this purpose as the simple solution of using it to switch voltage to the gate of a big MOSFET is inadvisable as any current leakage (e.g. due to surface condensation) to the gate terminal could cause the MOSFET to turn on, ignoring the reed switch. Using multiple reed switches in parallel to short gate to source to shut the MOSFET off when the lockout magnet is present would be more reliable, but I'd suggest duplicating the circuit (using the same lockout magnet position) with the MOSFETs in series, and even so, I'd want to open an access cover and physically disconnect power before working on propellers, any parts near them, or any other motorized mechanism.