I'm 5' 7", size 14-16 (sadly) and I don't have a very well defined waist. I've got an important social event at the weekend (meeting BF's family for the first time) and the party is on the beach with lots of kids. I want to be able to run around with them but also look really nice so I feel confident but I can't find anything that suits me. I was planning to wear a short dress with leggings and sandals with a thin khaki or denim jacket. Everything makes me look frumpy or pregnant. Any ideas? I've only really got today to buy something.