Well, from being in a horrible accident myself, the biggest thing I can recommend is to keep the inflammation down, which is going to be huge throughout his whole body. If he's inflamed, he's going to be just THAT much sore, as well as it will impede his healing process. He's gotta keep off inflammatory foods (so, basically a Primal diet plus no dairy or nuts), as well as take in foods with anti-inflammatory properties, such as coconut oil. He can take in the CO internally as well as apply it externally to his injury sites. It will be absorbed straight through the dermis very quickly.
He for sure is going to need physical therapy once he's able, and I highly recommend Rolfing if he finds he is having structural alignment issues and/or any sort of gait disorder that PT cannot fix. I did both concurrently, and both the PT and the Rolfer said they've never seen anyone progress as quickly as me. (My anti-inflammatory diet also played a huge role, I am certain.)
Sending my best regards,
"Let food be thy medicine and medicine be thy food." -- Hippocrates