Canon 5D Mark III Audio question

Hi there,

I will be purchasing a Canon 5D Mark III mainly for video production, and I just wanted to know if anyone could answer my question I have in regards to its audio capabilities.

I would like to have two separate audio inputs coming into the the camera. I would like to use a Rode shot gun and a wireless lav on two separate channels. Is this possible somehow? I was reading the audio input is in stereo. Is there a way to assign the shotgun to one side (ie. the left side) and the wireless lav to the other side? If this is possible, can I use a simple audio splitter and assign the sides internally in the camera? Both the Rode and the wireless lav will be mini jacks. Or would a basic audio mixer do the job to get both audio sources into the camera? Or am I at the mercy of an external audio recorder and have to sync them up in post? I couldn't find any info for anyone using multiple audio sources/channels with this camera. I am coming from using a larger video camera that had two separate audio inputs, and I found it to be really useful.

Thank you for your help and for a kind response:-)

Logan