One Tree Planted at Checkout

I like the idea of this app, but it needs work. I hate pops ups, so I will never use that option, it annoys customers.
The issue for me is with the widget. It should only display in the cart, it shouldn't show permanently on the site.
I also need to be able to alter the height of the part that pops out of the widget, as on mobile it cuts off the second button and you have to scroll to see it.
It ...

I added the app to our website and have since sold 50+ trees, however unsure whether the ‘order’ has been received by One Tree Planted. I have tried to reach out to the organisation with little response.

Obviously the concept is sounds however their follow up and action is lacking behind. I find the map on their website slightly misleading, I would like to have more traceability on their direct ...