I love the dress, and think it fits the dress code perfectly. My only concern would be if they're a "beige family". You know the type--everyone wears really boring beige clothes to pretty much everything. On every romantic comedy out there the rich guy/girl's family is a "beige family". If that's the case, you're going to stick out like a sore thumb. Not in a bad way, though, just in a noticeable way! (I'm this noticeably brighter person at lots of occasions, it doesn't bother me).
Also, where'd you find that dress?! I want one!
"I don't know! I don't know why I did it, I don't know why I enjoyed it, and I don't know why I'll do it again!" -BART SIMPSON