I was thinking the BP, a vest/waistcoat, a rustic, Jacobite style shirt, bonnet, and nice hose with either low cut mocs or ghillies....the reception is at a pretty "pinky-up" place (as my brother would describe). So I'm getting a custom vest made...and if I can scrounge some money I'm gonna' try to get either a new kilt (with a plaid) or pick up a plaid for my Irish National kilt...Is there a specific style of vest I should get?
You don't need a vest, new kilt, or fly plaid; you need a jacket (Argyll), a dress shirt, a tie, and a presentable pair of dress shoes, like black wingtips; the Highland equivalent of what the other gentlemen in attendance will be wearing.

No Jacobite shirts or moccasins.