I for one will be watching this thread!
Atmega 88 will work but cheaper to atmega328 ie Arduino (don't have to use Arduino IDE) Just cheap and no special programmers needed (unless fuses need to be changed)
or Atmega 2056 lots of serial ports so multi RF could be done but hard to do diy etch but lots of pins
Can't help with code but i would make my own hardware.
Wish you Luck, Phil