So exciting

We are having our photos done this weekend. Here is the situation: His mom is a photographer (not professionally, she does it on the side as a hobby), she offered to do the engagement photos for us. We are very excited! BUT.... We dont know what to wear, or what kind of pictures to take. Any advice for having them done? We will be on the lake shore in MI, which is beautiful!
I have other options if we want to get them done professionally but I know this means a lot to her. We just want to be sure we get good pictures.