When you open a pack, there are two tiers of Shiny Card, with different drop rates. Assuming you don't get a Rare "God Pack", the chance of getting any Tier 1 Shiny Cards is 3.571%.

To get Ditto in Pokémon Go, you’ll have to catch other Pokémon and watch it transform. Here are the current Ditto disguises, and how to get shiny Ditto.