Please advise... going to a fancy wedding

[TropicalHorse]

Hi all,
My first proper night out after the birth of DD is coming up and the invitation says "formal" which scares me! I have managed to buy a silk dress on eBay which is very nice, fits well and is actually flattering! It's similar to this one. I plan to wear it with a red strapless tank underneath because even when not breastfeeding I can't be as daring as this model! Can you stylish ladies please advise me how to accessorise - I need tips for colours and styles for shoes, a wrap or light jacket, and jewellery. I have short dark hair which I will pin up. Does anyone think it's too casual for a posh-ish wedding?

[LordPalmerston]

They say formal invitation what are the kind of wedding clothes are there? I think they sound like twats