I have to say that I have walked away from a few of these in the past. It's common practice. I'm afraid that anyone who buys ground or property carrying a covenant such as this, must accept that whoever has the benefit of the covenant, has control.
In a perfect world, these types of covenant would never be allowed. They're terribly restrictive, and cause all kinds of problems. That's just my opinion though.
I think your idea of a charitable donation is a laudable one. To be blunt though, it's irrelevant. Negotiation is the only way forward. Somewhere in all this there is a point where you are willing to offer a certain price..... and they are willing to accept it. It's as simple as that.
With no deal, you have a development, but with limited control, and they get nothing out of it. They would likely make your life difficult.
With a deal, you build freely and they make some money.
Which is why I tend to walk before purchase if no deal is likely.