I too don't like to show my upper arms (because mine are pretty "meaty" :teehee:)--in fact, instead of being sad when I see adorable sleeveless fashions, I no longer shun away from them, but I will buy them, and wear them with a cute shawl (or it is a great excuse to knit something fabulous!).
I don't know if a shrug would emphasize or de-emphasize things:think:. I think a shrug might be a nice idea because it would "stay put" better; shawls are my personal fave, but I have to admit that they tend to need to be put back into place quite a bit, something that you might not want to have to fiddle with during the ceremony. I like the idea of Knitty's Convertible--you can use it as either a shawl or a shrug; you might want to consider something like that because you can wear it either way. Just a suggestion. :shrug: