Help! Nursing mama while in a wedding party!


I'm a bridesmaid in my good friend's wedding this June. I'm currently nursing my 16 week old and pumping. Baby girl is not coming with us to the wedding, which is ok with hubby and I--we are looking forward to a couple of nights our! Here is my dilemma: my bridesmaid dress is chiffon and has a low back, so I need a bra that is backless. I've seen those sticky adhesive bras but I know I will leak at some points in the night, and nursing pads can't be worn with those bras. I'll be able to sneak away throughout the night a couple of times to pump, but does anyone have any suggestions on bra support in this situation? I have to bring my dress in for alterations, so should I ask the seamstress to sew in some extra suport? Thanks!