Either of your day sporrans will work. If you feel the black one fits best, wear it. "Semi-formal sporrans" to me are not worth thinking about. Save up for a formal one some day, but the nice black one will suit every occasion in the mean time.

You don't need "kilt shoes," either pair should be fine if they are polished and well cared for. Plain black shoes, like a nice black day sporran, are well suited to any occasion up to and including white tie.

The charcoal Braemar will be smashing. Go, and have fun. You might want to carry a dressy cane, in case the ladies become over-aggressive.