Wear what makes you feel snazzy! We just want everyone to have fun and be comfortable during this celebration. If you're looking for more direction, I'd say its dressier than jeans but more casual than an evening cocktail dress. Ladies, you may want to wear a more solid heel or flats to be able to walk on the grounds if it's a nice evening.
We will be covered in the church and barn, and both are climate controlled to keep everyone comfortable. However, for the short walk to and from your car, or to enjoy outdoor activities (such as yard games during the cocktail hour), you may want to bring a layer since we will be at the top of mountains and it can get a bit windy!