BM dress trouble!

I went shopping with my MOH (sister) and Matron of Honor (best friend) this weekend and it was tough. My sister is plus size and my bf is pregnant (but the wedding is 7 months after she has her baby). We are looking for them before the other girls, because it's most important to me that they are happy. We decided that cap sleeves/2 piece were the most flattering for them. My sister liked having the top piece cover her stomach.

Can anyone post pics/suggest dresses that will accomodate my 2 MOH's and look great on a variety of girls? We are going for silvery gray, if that helps.

Thanks so much for your help!