Thank you very much for your comments, ladies! They have helped a lot.
Barbara Diane, I am going to have to wear those shoes this time as I have no other walk-able dressy black shoes option. I will consider something more classic for the future.
Aly, I will make sure to pack my bag as lightly as possible.
Skylurker, thanks! I do not have matching pants for jacket #3, but I do have pants that go well with it. I am getting a pedicure today. And I wouldn't wear any of the dresses with out the topper (minus the gala dress) at a work function anyway!
Anchie, I do have some ponte blazers, but they are on the longer side and thus not quite right for dresses. I hear you on the patterned jackets, I have found a perfect little cropped plaid one but have to consider really carefully what I need to buy first.
Jenni NZ, you must a be a natural at professional dressing, then Thank you for the gala accessories suggestion.
Angie, thank you so much for all the help! Yes, I will stick to dresses for this conference because of all the reasons you mention. I will also bring a mini separates capsule ( 2 pants, a blazer and 2 blouses) just in case. I will bring some sheer hose as you recommend. I will worry about dressing for colder weather later. My most structured bag is the bone BR, so I will bring that one - it will also lighten all the black nicely. I will report on everything when I get back. I am leaving on Tuesday evening and coming back in the night between Saturday and Sunday.