Here is a simple, high side power switch that requires only 1 N-MOSFET, 1 P-MOSFET, 3-resistors, 1 capacitor and a momentary PB for control.
It is insensitive to the length of time the PB is pressed and also to any switch bounce.
The OFF power draw is only the circuit leakage current.
For supply voltages below 10V the MOSFETs must be logic-level types that fully turn ON (not their Vgs threshold) at the supply voltage (the Vgs value where the Ron is measured in the data sheet).
I...