I'm thinking of using a Raspberry Pi A+/B+ to pull the JSON feed and then use Python with the pandas library to convert to CSV and either throw the output onto the webserver or just have the ...

There's a jsonify function in Flask for Python, apparently (I'm not too familiar with Python, so I don't really know what using Flask just for this one operation would entail).

And there you have it: now you know how to open CSV files in Python! And with that, you’ve dabbled in your first bit of JSON development and even a bit of data science.