Looking at the green & white option - from a shop called Wild Clouds which I think was a recommendation on a thread here a while back. Jumpsuit
I think the wedding will be quite smart, but I'm very much there as a plus one. It's DP's niece, & while I like her & fiancé very much, she was an adult when we got together, so I don't know them well.
Unhelpfully, I have a very nice summer party wear jumpsuit that would be just the ticket, but it's got a black background, & really not wedding appropriate. I don't go to that many smart dos, so would ideally like to find something that would be wearable as a more everyday option in the future.
As a fallback, I do have a rather dated but definitely wedding-appropriate dress that I could wear, from when I was an age when lots of my friends & relations were getting married. DP really doesn't like it though - I think probably because I (a) rarely wear smart clothes, and (b) almost never wear dresses. Not that he ever objects to my outfits, but since I'm going as his plus one, I'd quite like to wear something which didn't weird him out 