Should i wear this to a wedding?

i know i asked what should i wear to my cousins wedding months ago. now i have another cousin who is getting married next month. my mom has all kinds of dresses but i need to try them on. i have two dresses. i can't wear the same one i wore to the other wedding. the other one is all black, sleeveless, with a long sleeve jacket. to me that just sounds plain and i feel it wouldn't suit a wedding too well. even though i will only be a witness. its a special occasion and i want to look good. i have to buy something a Khols because i was given a gift card. do they have dresses that would be right for a wedding? i think its going to be outdoors.