HS reunion ... what to wear?

It’s at a bar/ restaurant in the evening for appetizers with a cash bar... so sounds pretty casual. Is a sun dress too much? I just don’t have a ton of clothes that fit great right now and am not sure what I want to wear. I also packed jeans and a cute top, but the pants honestly don’t fit well. I’ve lost a lot of weight postpartum and my jeans are falling off (I haven’t bought new because I feel like I’m going to gain the weight back when the baby starts to wean)