Perhaps you could take a look at the link I provided earlier (MOS Trigger Switch Driver Module FET PWM Regulator High Power Electronic Switch Control Board  to determine if it would work as a PWM-compatible switch for our application
I wasn't real clear above - the following was referring to that module:
The FET driver module is triggered by a high logic input. This is not readily compatible with the decoder output, which will float when off, and be low when on, as I describe above. If you can find a p-channel version of it, you may be in luck.