Hi Sneaks, trousers and a top sounds fine to me. The most important thing is that you are comfortable, you're there, primarily to network, so you'll need to be able to concentrate on that - and your research, of course.
Academic events are rarely sartorial extravaganzas, in my experience, so I'm sure you will be up there with the best of them anyhow!
The lacey top and shrug sound good.