Definitely bring your contacts. Glasses just get in the way. I had plenty of time on the Doolie for a day to get ready. Well...plenty is a stretch, but I've been wearing contacts for years, so sticking them in wasn't hard at all for that morning.
However, (since there is always a flip side), it might be a good idea to wear your glasses, just so you can see what life will be like during BCT.
I echo everything Bailey said. I was in the same session she was and it was FREEZING. Bring your blanket and maybe some long underwear. It got to the point where my roommate and I were considering bunking together to share body heat.
And to further echo things said, SS doesn't actually gives you a taste of what BCT is like. At least, I hope not. I think it's more there to familiarize the kids with the Academy itself and to let them see everything. The things we were doing might be closer to what an upperclassman does. A very little bit of PT, classes, eating in Mitchell Hall, etc. The key phrase is laid back.