I think you need to take the lead from the type of wedding it is and whether the bride and groom have stipulated any dress code on the invitation.
I guess you know either the bride or groom, so I would judge your outfit dependant on the people they are. The venue they have chosen may also be able to give you an idea. A posh country house hotel or the local function room?
Your described outfit, sounds nice, but from my experience of weddings, it does sound more suited to a prom/ball.
And above all, you don't want to upstage the bride!!!