Gate-Souce resistors needed?
IF the drive sources are always high or low and never floating then R2 R3 R4 are not needed. 

If any of these are sometimes open circuit / high impedance then IF you care that the FETs may turn partially on and stay that way then the pull downs are needed. 

Really only R2 is enough as Q8 Q9 do nothing if Q6 is off. As current per resistor at 5v drive is i = V/R = 5/100k = 50 uA then odds are this will not make a lot of difference (20 hours per mAh) UNLESS the low or high drive is left on when the 38 kHz is off/low. 

As others have noted  - you can save an I/O pin, a FET and a pulldown by having low power setting set by a resistor where Q9 is and add to it with Q8 as required.