Congratulations on your upcoming wedding, Luckykelleyk!
Hmm, with that lovely dress . . . so many possibilities! Just some thoughts . . . .
I would have been tempted to say no necklace if your earrings were going to be the chandelier type (maybe a bracelet instead), but with the classic style you described, you could go either way.
For a more traditional look, maybe a single, choker-length strand, around 8-9 mm (or perhaps a bit larger). Something like this, maybe slightly longer:
http://abcnews.go.com/Entertainment/CelebSnapshots/popup?id=3586942 (Grace Kelly)
A double strand nesting at about 16 and 17 inches or so might also be nice - I think a lot depends on how everything looks with the veil and tiara (if any). Here is C.Z. Guest in a double strand, a little closer to the neck:
http://www.style.com/beauty/icon/111203/ (C.Z. Guest)
Another option would be a graduated strand, which has a more vintage look (I believe Jackie Kennedy wore something similar in a choker length at her wedding):
http://www.weddingchannel.com/ui/buildArticle.action?assetUID=3363 (Jackie Kennedy)
Terry at The Pearl Outlet has graduated strands (also in lavender!) - his are a bit longer but they can probably be shortened:
http://www.thepearloutlet.com/servl...eProcurement&supplierID=490&commodityID=29209
As for color, my personal preference would be white - I think a bridal look of white with just a hint of color (your bouquet) would be stunning. In general, I think fewer colors = more elegant (same with jewelry - often less is more, unless everything coordinates perfectly), which is why I think so many brides choose diamonds, white pearls, and white gold or platinum - they add sparkle and luster without detracting from the overall impression of bridal white. But I admit to being a traditionalist when it comes to weddings! I'm sure there are many other equally lovely possibilities, and I agree with the above posters that you should do what seems most beautiful to you after trying various options with your ensemble.
I love that kunzite, though, could see it as a focal clasp worn in the front of a multistrand lavender necklace - wow! How about two necklaces? One for the ceremony and one for the reception?
Congratulations again!
Perle