You can wear whatever you want to a meeting like that, but I would go knowing there is a general sense of modesty in dress in the LDS Church that is more conservative than many other places. Jeans, dress slacks, khakis, moderate length skirts or dresses, full shirts of any kind, t-shirts, etc. are fine, as are shorts that go near or over the knee – but you probably won’t see many, if any, tank tops, mid-thigh shorts or skirts, spaghetti straps, etc.
Most members really are friendly and caring, but we have our collective hang-ups when it comes to how we dress – and it’s a near obsession with some people, especially older-generation adults. You need to know that upfront.