I did my scafoid (Sp) and both elbows 5 1/2 years ago now.
It really does depend on how good he was before hand. I was driving a car two weeks later, but took 3 months to get back on the bike. Had an operation after 4 1/2 years on one elbow to remove bits of bone, and another one to try and fix the damage done to my shoulder (which wasn't apparent at the time, due to the elbows)
Its the little things that you wonder how to do, without both arms, like going to the toilet, eating. I was lucky I was only in a case for my hand for two weeks, started physio a week later.
By the sounds of it, he got off a lot worse than me, but may have the use of one arm soon. Just don't rush it.
The best thing I did to get almost all of my movement back in both elbows (radial head fractures) was to get plastered. Next morning my movement had improved dramatically. Though still not what it was, and never will be.