I am bridemaid for my cousin in June and desperately need to know what shapewear would be suitable?

My family swears by Spanx. However I went to Walmart and they don't have that brand. I picked up a nude brand called Sweet Nothings. It seems really good--I tried it on with my dresses for the cruise. I'm going with my family in a couple days and my mother is the one who will never p up an opportunity to commit that you look like you've gained 5 lbs.