How to switch dummy load circuit on/off with pwm?
If you wish, you can buy logic level mosfets that are intended to be controlled by 3.3v or 5v and use them directly in your circuit.  You can also get mosfet drivers with a variety of functions.  

Check out a MIC4426/7/8.  You can use it to speed up switching and drive the gate of a 10V Vgs mosfet with a logic level (5v) circuit.  You do need an additional source at gate drive voltage.  You can also get boosting mosfet drivers that create a drive voltage way above the positive rail for you, so you can drive N mosfets on the positive side of the circuit.