Semi-formal or cocktail attire- something that you feel nice in.
Why at a church?
In short, we're not getting married at A church, we're getting married at THE church. The First Unitarian Church of Philadelphia is a regional community center that provides meeting space on a non-discriminatory basis for many different groups and activities, including cultural, educational, civic, wellness, and spiritual activities. Additionally, they have hosted legendary punk shows which we have both attended many of throughout the years. It's a cool church.