The good stuff
The movie's strongest message is that everyone is both good and bad, light and dark, and those who love you accept you completely as both.
What to watch out for
Shaw puts his love of money and possessions above all else. Alexander might have stolen from an awful man, but he's still a thief, and Elise is a rogue character who makes questionable professional and personal decisions.
A kingpin and his gangster henchmen try to kill Frank and Elise several times, chasing them on speed boats and through the streets/rooftops of Venice. A man is throttled to death, and four or five men are killed by police snipers.
Elise is pretty much sex appeal personified. She's presented as being so stunning that men and women stop in their tracks to stare at her as she walks by. One of the uses of "f--k" in the film is inspired by the sight of her in an evening gown. There are a couple of passionate kisses, as well as one scene of Elise changing into a lacy nightgown (viewers see her in her bra, stockings, and underwear).
Occasional strong language includes a couple of uses of "f--k" plus "a--hole," "s--t," "h**l," "ba***rd," and "oh my God."
The Eurostar train system is featured pretty heavily, and the logo is shown a few times. Venice's ultra-luxurious Hotel Danieli is one of the movie's main locations.
Drinking, drugs, & smoking:
Several people smoke cigarettes, and Frank smokes nicotine-releasing electric cigarettes. People are shown drinking socially at dinners and a party.