I would use a tool like this. https://www.amanatool.com/49501-carb...l?ff=1&fp=7281
Standard corner rounding end mills don't work well in aluminum, I have a couple of sets of them and never did like using them even in steel. I normally default to carbide tipped router bits for use in all metals.
Just remove the bearing, and grind off the bearing nose. I use the 1/2 shank where possible, but 1/4 inch shank will do in a pinch. Bump up the spindle speed a bit and apply plenty of coolant.