Well, if you want to engrave, you know as well as any the YAG is your only option (with what you have in house)... the CO2 is out of the picture (unless you want to mask, cut with the CO2, then electro-engrave). With a proper fixture, you can engrave in one area, shift, then engrave the next area over... but your fixture will need tight tolerances to avoid seeing any gap or overlap. If the engraved area (to depth) is large (you mention circular marks), you could simulate that look with some final passes of the YAG on a lower setting in a circular motion. Don't know how it would look, but with some tweaking you could probably get it to look about right.

Or maybe a steel stamp and press would give them a fast engraving (if the aluminum alloy is soft, the stamp wouldn't have to be terribly hard/expensive). Though you would get the circular pattern without a lot of extra work on the stamp, and I'm not sure that kind of detail would last very many stampings.