An Argyll does look good with a vest but obviously that would affect the exposure of the shirt as it would be more hidden.

If you don't wear a vest you can wear a belt with your kilt and Argyll - if you go for a vest then omit the belt.

I have a PC already so would wear that at a wedding as I will next month at a Civil Union wedding I am attending but if you haven't already invested in a jacket maybe you should defer to your other half.