Now I got the server code up and running written in python 3. I can now use my app to send commands to the RPi and then to the nRF24 lights. In a couple of days I'll make a short video of this working and upload the code to GitHub. In future versions of the server code I'd like to add presence detection and sending data back to the phone.
I'll also be making one more revision of the receiver PCB for easier assembly and programming. Moving all the parts to one side, removing the crystal and changing the 3pin to a 6pin programming header. Also possibly breaking out some unused pins from the atmega if there's room left.