Screw your neighbor and even what they are thinking,,,,,,,,
I hope people don't go this route. My dad thought like this and and one brother does too. My mom didn't, and I personally don't prefer it. My current neighbors aren't like this. If you make your bed you have to lay in it. "Never be alone?" That's a bit much. That's not my America, NOT what I will teach my kids. But keep in mind maybe your neighbor was raised like this.
WoodchuckDad maybe you can look at the area (where neighbor made his mistake in house placement) as generating a different form of revenue. Perhaps a much EASIER type of farming - grow BUFFER! Lets say they would like to preserve the buffer (perhaps while they enhance their own buffer). Tell them the land they want use of, will produce $XXX of apple profit per acre per year. If they want use of the land they are welcome to lease it from you for $X,XXX. If they decline it becomes their decision, and there is no bad guy. If they want to do it for a few years then they can make that decision every year whether it's worthwhile. When they tire of paying (which could be before even the first payment) then you can expand the orchard. You get the same money for less work, less chemicals too. This becomes their way to "let go" of the neighbor property they THINK they own.
For you, the 5 acres begin to produce revenue from day one, before the rest of the orchard has the first apple. This will be useful to you, it could pay startup costs. My guess is that they will decline, and seeing the ball in their court, will let go of their notions.
The cost of this project is their responsibility not yours. Tell them you're willing to do the footwork to keep everyone happy, but not willing to pay in lawyering (or in apples). YOU contact the lawyer, don't deal with theirs. A standard lease can be adjusted in one hour. They don't get rights to do anything on the leased land, their only right is prevent cutting of trees while the lease is in-force. You can make it whatever you want, 3 years then year-to-year thereafter. And you can use the land as a wildlife corridor as you planned. Just keep quiet and let them talk about their needs ONLY. Don't admit to ANY benefits that you will enjoy (less work or wildlife).