Yeah had a friend who got caught being really stupid a few years ago... (Michael Milken was a bad bad choice as a mentor) The federal pen isn't really hard time.
If he's going to the federal pen in Danbury, it's a prison, but it's not Rykers Island or some of the other hardcore prisons. danbury is sometimes referred to as a country club because the living is pretty easy. it's no picnic though either, but the chances of being knifed in teh shower are pretty slim.
His wife and kids are going to have it the roughest because there will be people who will treat her like garbage... Be a friend to her, and to the kids... Help out with the manly things around the house... (fixing stuff etc..)
If you have it in you - -visit him if you can - write letters to keep him in touch with the goings on in the world.. Dont spy on his wife (not that I think you would)
and good look to your friend...
If he's got a sense of humor - get him a copy of Andy Borowitz's book - Who moved my soap?