First, cute dress!
I would do the tights and low heels or even cute flats if you want to be a little more comfy.
I think because the dress is already knee length that tights/boots are going to be a little too heavy of a look, especially with the large belt accent.
I LOVE the necklace! I would wear it how the model is, under the collar of the dress so you have some fun sparkle peeking out. You could do a bracelet too, like PP suggested but I wouldn't do anything more than a stud earring if you go with the necklace.
So jealous - sounds like a fun event! Have a great time!