I wouldn't get a cone that large. As a matter of fact, I wouldn't even get a grinding cone like that at all, because your wheels are made from aluminum and it'll gum up in that grinding cone super fast. I'd get a burr bit made of either high speed steel or carbide, and run it in a Dremel. Something like this
Most likely outcome is that you're successful but the chamfers are uneven. Burrs are pretty easy to use but it's practice that gives you a consistent profile.