Advice needed

[Cephas]

My advice would be to double check with your cousin. See what the men in the wedding party are wearing and that will give you an idea of how much you need to dress up.

Informal can mean different things to different people. I did a wedding for a couple once where informal meant "no tuxs" and the men were in suits and ties and the bride had on a simpler white dress than the formal wedding gown. The next wedding I officiated at was also "informal" but there there were no jackets or ties to be seen (lots of t-shirts and sandals though).

A white shirt and tartan tie sound like safe choices. If you add a vest to it I don't think you would look too "formal". But then again the joy of a vest or jacket is they can be taken off and left in a car if you think you are overdressed.

[slohairt]

I should probably amend some of what I posted. You can wear a waistcoat alone, but it should be the type that has a full back made of the same material as the front. If the waistcoat has a satin or silk back and an adjustable strap, it is meant only for wear under a jacket.