I called Newhaven Display this morning and talked to an application engineer. He said that particular display would be usable at 3V3 and about 0.1V on V5. He also said that to extend the viewing angle you could apply a negative voltage to V5, for example, around -1V with respect to ground.
If the chip on OP's 3.3V Mini-Pro is an ATmega328P-AU like shown on Sparkfun's page, it is rated to 5.5V.