@potatotron:
Many thanks for your Photon recomandation. I'm not a big fan of cloud IDE neither but, as they have noted on the product documentation page, you still can compile and upload your sketch locally (using dfu-utils) hence chances are your Photon may live after their cloud are out of business.
@defragster:
OAK looks promising but is just as featureless as any other current ESP8266 single board implementation (only few GPIO pins available, only one ADC input and so on).
By using Teensy for awhile, I'm accustomized with having lots of features (thanks Paul) to accomodate with any small-medium scale project. Beside, I only found available the two aforementioned boards (Photon and WiPy) thus I have to make a choice for one or another.
Once again, I'm talking about a little educational project (an introduction to the embedded/IoT concepts for my son) hence he needs an easy access to an IDE and a simple uploading procedure (+1 Photon).
He already have some past experience with lua/python scripting for Minecraft hence the WiPy board (micro python) could be an attractive option, too.
I may end up buying both boards as I can't afford to ruin his Christmas holiday with a wrong choice.