I wouldn't bother actually making cuffs. What you can do, is simply get some matching colour braid (the twined, ropy stuff), running several pieces vertically from cuff end, up to where a cuff top might be. Then, attach your buttons on the top part of each braid. That will give you the double-cuff look. Now, did that make sense at all?

As for the vest, with the peak lapels you have, I would go for a vest with no lapel, or one with a shawl lapel without the satin. It should be one of the styles with only 3-4 buttons on it, so that more of your shirt is showing for formal. For less formal, get a second vest with more buttons, same as you might have with a 3-piece suit(do they still make those?)