Upload & Sell: Off
I have owned both. first off, the proper etiquette is doing your price negotiation before hand, as you have done. this happened to me once, when I met with someone, who said he is interested in a lens, and then offered me less, and really pissed me off, b/c it was a total waste of my time.
Back to the lenses. 16-35 1 is a great wedding lens. 16-35II has better corners, esp on the wide end, which should be of no consequence for your application. the version 1 may be even marginally better wide open on the long end (28-35). I think the extra stop is very useful for indoor weddings. as for copy variations, I only owned one copy and it was very good.
Tokina 16-28 is another option, bigger and heavier, and more limited range, and a protruding front element. definitely will be sharper wide open in the corners. in the center, on a 5d2, not sure if there would be any visible difference. It is also subject to QC variations according to every review I read.