Don't worry about looking overdressed in the church - they're always freezing so you'll probably want to keep your coat on the whole time anyway. As long as you don't turn up in one of these I promise no-one will give you a second glance.
Try on the blazer and see how it looks - velvet is nice but not if it swamps the shape of the dress. The cardi sounds like an OK alternative but not as smart. Black satin peep-toe shoes will be fine with black tights, if you want to wear skin-coloured you'll need something with a closed toe.
I think that dress is fine for a wedding, especially at your age. I second the advice not to go overboard with accessories as the neckline is detailed. As previous posters have said, it will be cold in church so you'll have some kind of cover up on so the dress will be fine. Have a lovely time!
She's not going to the church bit, just the evening.
It's lovely, you'll look lovely. I wouldn't bother with a blazer or whatever, you'll be too hot if you're dancing. Just wear a coat and take it off when you get there. Agree with pewter heels, but I think copper, (dark) gold or silver would also work. If they're closed toe, go for nude tights. If they're open toe, either get those open toe special tights or I'd risk it bare legged (but fake tan!!!). It'll be dark so no one will be inspecting you.
Evening do of a wedding is just like a dressy night out (but no jeans). Don't panic!
Sorry, just seen the church bit. Got confused with the not going to wedding breakfast. So - you will need some tights and you will need something extra up top. What about a nice cardi? Or you could even just wear a silverey pashmina.
Well I'm 34 and I'd wear that for a wedding. Team it with plain shoes and jacket/cardi and you'll look lovely. Agree with not to much jewellery/accessories although I reckon you could get away with a statement ring.
It's lovely and absolutely fine for a wedding, including church! I've been to loads of weddings in the past few years and lots of people wore similar style dresses, just keeping their cardi, jacket, shawl etc. on in the church or registry office.
Sorry got to go against the grain here and say it looks like a dress Ann Summers would sell. It's a prom dress and to me it looks it - something a 16 year old would wear to try to look hot. And dark shiny fabrics totally inappropriate for church, I'd say.