Project advice - Transfering data to a remote uC and a RFID reader.

For my next project I will be communicating with some SPI devices using the HW SPI on the ATMEGA328 within the same PCB.

My issue is that i need to set up an SPI RFID reader and a few extra I/O's about 5 meters away from the uC.

First toughs were to configure the serial port as a secondary SPI port and run that at a lower frequency that would not cause any issues with the long distance.

I could also set up a second micro controller to read the peripherals and provide the extra I/O, communicating via true RS-232 at +/-12V. This will give a bit more work tough.

Or perhaps i am missing something altogether and someone can come up with a better idea.

If it were YOUR project how would you do it and why? Any advice appreciated.