Good fences make good neighbours

I fully agree with that sentiment - especially when it comes to being a pool owner, in which case, fences are not just ornamental or a boost for privacy, but are a safety feature. Steve's family has experienced the lifelong trauma of losing a child to drowning. We will do our utmost to ensure our backyard is a safe place, including unclimbable fences and self-latching gates and doors.

But we have a problem. There is a beautiful tree in the very centre of our backyard, right on the property line. The current fences (yes, there are two - I'll show you in a bit), cut right through the middle of it. I love that tree. It gives shade, and green and privacy. It is beautiful. Plus, it suspends one end of our beloved hammock. Our plan is to keep the tree, and on our side of the fence, it's safe to do so, but there's a hitch.
Looking at that picture ^, you'll notice that any ten-year-old could probably climb the tree on our neighbour's side and hop the fence, no matter what kind of fence we install. We spoke to our neighbour yesterday, and they have no intention of doing anything about the tree on their side of the property. They implied that, if we put up a new fence they would probably take down the old one. (But no gesture of splitting the costs of said fence.)
So I'm trying to come up with some non-ugly - maybe even esthetically pleasing alternatives. What if we built a secondary wrought iron fence well inside our lot, just around the tree, so kids could climb the tree, sure, but then would have to scale a secondary fence? How weird would that look? We'd still have to cut down our half of the tree, or kids could use that half to climb the second fence.
Have any of you seen creative solutions to fencing off pools around trees?

(And here's a close-up, so you can see the ugly little metal fence that the tree has also grown right around. It doesn't make any difference to the fence challenge, but I thought I'd show you one more of the ugly things we've found.) And, finally, as a "Sunday smile," here is an example of bilingualism failure. Today, Steve is putting up blinds in the kitchen. They came with a small box of parts. Printed on one end of the box was this:
Fair enough. So he turned the box over. And saw this:
Which (for my English-only friends) means, "Open at other end," thus rendering the instruction completely redundant. (Or perhaps they really meant for English speakers to open it at one end and French speakers to open it at the other?) It reminds me of one of Brian's favourite practical jokes: he writes "Please turn over" on both sides of a blank sheet of paper, then watches to see if anyone will get caught up in the turning-over loop. Silly boy!
I wonder how many times Steve turned the box over before he gave up and just opened it.