Design of social media cards/posters

We are a small charity looking to run a promotion on social media. I need 3 cards designing to use, I need 3 different photos sourcing for the cards. In addition to this I wish to have the cards printed to display at an exhibition in large poster format so they need to be designed so they can be printed too.
I do have a strong idea of what I want but it is included in a larger document that needs to be emailed. I need the work completing by 14th September