Spring Weddings

What should I wear to an afternoon Spring wedding in March?  My date is going to be a part of the wedding party, so I want to look cute enough paired with a tux, but since I'm just a plus-one, I'd like to be low-key.

Some retro pieces cute enough for Spring.  Inspired by Kelly Osbournes' style.

 

 

I especially love the black & polka dot dress - the silhouette is classy and chic while the polka dot is very retro.  By the way, you can find these great vintage styled pieces at ModCloth (started by fellow CMU alums!).

Or, should we go with slightly more timeless city chic formal:

 

 

The bright blue dress has delicate trimming around the neck and black piping along the bodice, giving it a slightly more modern look for an otherwise original dress.  The styling for the flirty-winged beige dress is a little awkward, but the silhouette is very elegant and ladylike.  The red heart-applique dress actually has cut-outs of hearts - the most darling of all! 

Some close-ups below:

 

I also adore this pink dress and its cut-out back:

 

All city dresses by BCBG.

What would you wear to a Spring wedding in the afternoon?