I can see, now, what you meant about "no fences allowed". It makes for a tidy neighbourhood, but I would resent the lack of privacy. I love the curvy beds. I never "do" symmetrical.
Can you put a very close to the ground barrier, just to delineate your yard, without violating your bylaws? Even pegs and a string a few inches off the ground? I can see why your neighbour children think it's OK to just wander onto your lot, without there being anything to say, "your yard ends here, this is MINE". Having something there would let you teach Sniffers the same, too. Not secure enough to leave him out there alone, of course, but maybe enough that you could play fetch off-leash once in a while. I've never taught boundaries that way, but I've read about it being done. Kind of like a mental e-fence!