I used EasyEDA to design and order through JLCPCB a PCB for the sensor nodes to fit into the Hammond 1551V size 2 enclosure. I could have done the minimum order of 5 boards for $2 (and probably will go that route when it comes time to order a board for Dwalin), but since I can easily see using 5 of these, I wanted to have plenty - so I ordered 30 for a total cost of $13.05 shipped w/ DHL. 

I set it up for I2C to two different headers, one with the pinout for the OLED modules I have and one with the pinout for the BME280 breakout board module I have - between them they don't have the same pinout for Vcc and GND. I set up for either two pushbuttons or for an encoder. I set up a serial port (GND, Vcc, TX, RX). I also set up a second set of headers inboard of the headers for the ESP8266 module (it's roughly Wemos D1 mini sized, but slightly smaller), and finally a 2x3 header to bring out a second set of pads for the pins I'm not making any use of. 

Since this board has at least two pads for every pin, I think I'll be able to use this for prototyping other projects in the future.