Cavscout we have done almost the EXACT same thing with those jackets. My lady had some faux silver buttons she's inherited from grandma, and they're now adorning my Eton. I orderd some smaller round, pewter celtic tri-horse buttons off of ebay. There are three on each cuff, now. I ordered a wool, cutaway three button bare-backed vest from the Uniformal Wearhouse last week, it should be here any day, now. It was about $40 including shipping and has satin lapels. I will pull the black buttons off of the vest, replace them with some of these smaller pewer celtic buttons and the formal getup is all set.

.....pretty much *exactly* what you're doing.