Running from 9V, you definitely need R1, R2 to be 2 x 1K. However, your schematic is wrong. They need to be in series, not in parallel, and the gate drive to the P-channel mosfet needs to be taken from the junction of the two.
I would connect the 100nF capacitor to the source terminal of the P-channel mosfet instead of the drain terminal, and put a much larger electrolytic capacitor (e.g. 1000uF) in parallel with it. Position the P-channel mosfet and capacitors close to the 9986, and keep the traces connecting these 4 components short.