UI design for binary decision

We face an issue with how to design the UI for a decision step in an android app for a selective, professional user base:

Whilst fulfilling jobs using the app the users will come to a step where they have to book a decision into the app. A decision between "yes, I will go on with a positive choice and proceed to the next step" or "no, there are objections, I will cancel this process and confirm cancelling here and now". So both options have a different flavor as to how the app proceeds.

Traditionally we are using floating action buttons to confirm something, so we started out with such a button on the bottom right corner to allow to confirm the positive option. Works fine, obviously.

The issue is the negative option. Offering an additional floating action button in the lower left corner is an obvious approach, but we need an additional confirmation to book the calcellation. We do not want a confirmation dialog, though (soo slow, too ugly). So we thought of morphing the button... but into what? And how can you deactivate the morphed button again if you reconsider and do want to go on with the positive option?

Are there any best practice approaches for such binary decisions? Any widgets typically used for this? I thought of the android "accept incoming phone call or decline it" slider we all know, but that is so fiddly, I often experience issues using it. So I am not happy with that...