Beach formal dress for the mother of the bride?

I suggest she wear something comfortable :P I know it's a vague answer but it's a wedding and she's so concerned about what to show and what to hide, it's easier if she can simply find a nice dress that she could freely move in with. The more comfortable she is, the easier it will be for her to enjoy every moment of her daughter's wonderful celebration. But to speak about designs - why not wear a sleeveless beige gown. Something that has heavy decorations (sequins, beads, bows, whatever) on the bust area and on the sleeves - this will draw the attention from the belly to the bust. Then wear a shawl to cover up the arms. This will prove to have a nice effect with the beach atmosphere. Wear fresh white flower/s for the head piece. This also goes nice with the motif. Thanks for the response on my discussion :)

I suggest not to let her wear sleeveless. To hide her tummy, let her wear something that will balloon on the lower part of her body as a design. It should not be totally flowing. It should be tight on the waistline.