Battery and Voltage Regulator for ESP8266 and HC-SR04
That sounds reasonable. The only issue is the necessity of a couple of voltage converters. The other choice is to have 5V step-up converters and a 3v3 LDO for output.

An alternative approach, I used, is to use a (locally available) 4v1 1000mAH VRLA battery with 6V solar panel and a couple of Schottkey diodes. I used a LDO (XC6206 - datasheet here) to ensure a 3v3 Vcc (or Vdd).

If finding VRLA is difficult, a Li-ion or Li-po could be used, but you might need a charge controller (e.g. TP4056 - datasheet here). That's why I prefer VRLA batteries as they are more forgiving with the charger circuits.