Power MOSFET or Relay
If you have access to the ground (more accurately, negative) side of the load, you could probably use a smaller N-channel FET than the P-channel that you have because of the way that FETs work.  Something like this:







simulate this circuit &ndash; Schematic created using CircuitLab

Don't forget D1, regardless of how you control it.  It limits the voltage spike when turning off to a diode drop above the supply by providing a path for current to continue flowing through the inductive load for a (short) while.

If you must control the positive side, then your PFET circuit looks good, except that your R18 is 220 ohms with 12V across it when the motor is on, which comes out to 0.65 watts.  With that value, I would not go any less than 1 watt, but you should probably look at a higher value instead.