It sounds like you have 2 Shipping Profiles - a free shipping Profile for the 2 products, and then your General Profile for everything else. If that's the case, unfortunately, there is no way to offer only the free shipping option when you have a mixed cart using Shopify's native shipping features. When products from multiple Profiles are ordered together, Shopify combines them into a single rate.
With Intuitive Shipping, you can use just one Shopify Shipping Profile, then create a Shipping Scenario with a condition that states if any item in the cart is Product A or B, always offer free shipping.
If you would like to give it a try, you can install Intuitive Shipping from the Shopify app store for free, and use the app in Setup mode for an unlimited time to make sure it's a good fit for your shipping requirements. We offer a 14-day free trial if you decide to activate.
If you'd like more information about how Intuitive Shipping works, you can also book a demo with one of our team members to learn more.