Days until deadline: 16
I still don't have the correct tag in hand yet (ntag203). But today I was able to write an NDEF formatted message to the MiFare Classic tag that came witdh the NFC reader. This was all thanks to the Seeed Studio PN532 library which includes the NDEF library which https://github.com/don/NDEF.
I also took the time to write a Python script that is able to generate the unique strings. It also formats these as a C header file to be stored in PROGMEM of an Arduino. These is also a test sketch to make sure this is working with the Arduino. This is available at the GitHub repo.