You Mean We Have to Dress Up??

I am trying to come up with some cute costume ideas for really cheap for all my siblings. We are having Halloween at our house this year just because we always go over to my mom's house. We are having dinner and then going trick-or-treating. Jason and I bought my little sisters costumes last year. I was just trying to find something that they could dress up as this year.

We have our really nice red dresses that were supposed to be for my mom's wedding that never happened. So I was thinking that we dress up as those ... and if my brothers wanted to they could dress up really nice and we could say we are all wedding singers. I thought it would be really cool. But it's not jumping out at me like a great idea. Got any ideas??