PaulRB:
Well, an esp8266 chip does not have a 5V pin. Esp-12 modules don't have one either. So what are you really using? A NodeMCU? A Wemos Mini?
Correct - NodeMCU. Eventually, I'll be wanting to put the ESP8266 on a PCB by itself, however, so I imagine I'll need to have whichever step-up device I use in-line between the power supply and the sensor? And then a voltage regulator between the power supply and the VIN on the module?