Dress Dilemma

I recently talked about our bridesmaid dress search here.  After days of going back and forth and looking over all of the pictures, we decided on the dress below.  We thought it was the most flattering on everyone.

However, after showing the dresses off on my go-to wedding site (weddingbee.com) I got some comments back saying that they weren't formal enough to go with my dress/wedding.

Here is my dress/some pictures of the venue (see more pics of the venue here and read more about it here).  We are going for a traditional type wedding and it will be starting at 2PM on a Sunday.  

So are knee length dresses formal enough?  What's your thought?  Yay or nay?