Discount for 2 Products in one category

Site URL: https://flyhighyoga.com/shop

Hi all, 

i have an online shop with two categories (Accessories and Trainings). Each of the categories includes 3+ Products. 

For a marketing campaign i want to offer a discount on selected items. To be more precise i want to offer a discount for 2 Product of one category (which has 3 products) AND i want to only have one discount code.

Options i can: 

• add discount per product (would end with two different discount codes, which i don't want)
• add discount per category (this would include more products as i want to include) 

What want: 

• one discount code for two different products of one category (where the category as more than two products)

How can i solve this problem?

Any hints and help is appreciated.