Hi, Nathan!
I’m Shay, a Guru here at Shopify.
Product Bundles could do the trick, I do know specifically that Product Upsell (https://apps.shopify.com/product-upsell) will allow you to trigger an offer based on clicking the add to cart button on a certain product, so that could be the best choice for you overall :). It's got a generous 30 day free trial, so feel free to download it and try it out to make sure it's the one for you!
Hope this helps!
Happy selling :)
Shay
Guru | Shopify
