Fall Cocktail Dressing

I am planning a small, intimate Saturday early evening gathering at the cabin later in October.  It won't be huge, 20 or so guests, but I somehow want to stress that this is "cocktails" and not have anyone show up in jeans.  How do I do that in this day and age when so many people lack manners and gracious style? What would I like to see the ladies wear?  Here are some ideas........am I dreaming?

While I think Tory's dress is lovely, it fits New York, but not Virginia.

I'd prefer this....

(Anthro)

(Anthro)

Or I'd wear this top with skinny black pants and a great gold necklace.

(Top)

(Talbots)

(Kate Spade)

(J Crew Dress)

And I adore this outfit. Less is definitely more!  The pearls, the simple white t-short.  Add a long sleeve cashmere t-shirt for colder weather.

(J Crew)