It depends on what you're comfortable with. There's no bad language or sexual content, but it is a first person shooter, so lots of guns, guns, guns.
However, you're primarly fighting against aliens (Fallen are four armed lizard people, Cabal are giant humanoid turtles in steroids, Hive are vaguely demonic looking humanoids with three eyes who occasionally fly, Vex are robots) in the PvE (player versus environment, so against AI opponents) missions that make up the bulk of the game. Occasionally their noggins explode after a head shot, but it's not gory - it usually looks like gas escaping, rather than blood. I'd say content wise it's probably less gory than the Lord of the Rings movies.
In the PvP (player versus player) modes you're fighting against other players who are humanoid, but again, it's not gory. As with the Star Wars Battlefront query, the main concern will be voice chat with other players, but it's set to off by default in Destiny.