Harry Harrison's "Stainless Steel Rat" series is a good possibility, although you may want to vet it yourself first; Jim DiGriz is a cheerful criminal in a society where there is almost no crime remaining. It's a hedonistic romp through the galaxy, with his own perfectly rational justifications, of course, but he is not violent and in fact hires on with the intergalactic police to catch a violent criminal they're having a hard time with. For all but the first book, he is working for the good guys, but he keeps his fingers in the till along the way.
I can't recall exactly how much sexual reference there may be, but I don't think it was much, overtly.
If he's into any kind of fantasy, there is Piers Anthony -- the Xanth series is horrifically punny; the Apprentice Adept series part SF and part Fantasy and lots of fun, about a planet that is scientific with a hidden alternate reality of magic; the Incarnations of Immortality series is about the beings that inhabit the personas of Death, Time, Fate, War, Nature, and Good and Evil, also quite fascinating and fun; the Geodyssey series takes one family from the beginnings of prehistoric man all the way to post-apocalypse -- the same people feature in each chapter but move along in Earth's history, if that makes sense -- it's great if you're interested in the progression of civilization and language, and a good story to boot.
There is also Robert Asprin, the Myth series, if he's into punny fantasy.
