One thing I have brought with me after my first track day is a 1/2" ratchet and a 19mm socket to tighten the lug nuts after the first few laps, just in case. I would recommend topping off coolant the day of/day prior, same with oil. A tire pressure gauge is also a good idea, although I'm honestly not sure where the nearest place to fill is there. For the helmet, get a nomex head sock. You can wash the sock, not the helmet. Plus fire sucks. My two cents on the whole thing.
For the GoPro, I have adhesive mounts I'm not planning on using, I'll bring one or two if you want to use them. Like jacket_man said, recording devices are prohibited, so use at your own risk.
<borat>I am excite!</borat> I believe myself, wrxfr3ak227 and Goe are headed up tomorrow in the afternoon, good nights sleep and all that. Awesome to see another STi in the mix.