Jerry,
From the schematic at http://ruggedcircuits.com/AM040/am040.pdf, it seems that the Hibernate (pin 20) of the Microchip WiFi module IS connected to the Atmega328 onboard, and it seems it is connected to D8. Try something like:
pinMode (8, OUTPUT);
digitalWrite (8, HIGH);
to Hibernate the WiFi, and:
digitalWrite (8, LOW);
to wake it up. Let us know how did the module behave.