You don't really "use vital strike as a standard" - you can use Vital Strike when you use the standard attack action.
The standard attack action works the same for all kinds of weapons, including natural ones. You choose one weapon/natural attack and make a single attack at full BAB with it.
For Deinonychus, a standard attack action with Vital Strike would naturally be a talon, so it would do 2d8+X damage.
Yes. It'd work the same way as it does for any other character. For example, a druid wild shaped into a tiger with a post-wild-shape Strength of 18 normally claws for 1d8+4 and bites for 2d6+4. If the same druid has Vital Strike, she could instead either claw for 2d8+4 or bite for 4d6+4.
This gets interesting when the druid is a cave druid. (A carnivorous crystal's base slam damage is 7d8....)