I think the single best thing you can do, is once you get to the BIL's, drink a lot of water. When at high elevation, you can get dehydrated quickly. It's very low humidity, and your sweat can eveaporate without you knowing you're sweating. Drink lots of water. (And continue while you're here)
Also, as you noticed from the weather forcast, there will be a serious temperature swing between when you leave at O dark thirty, and the middle of the day. dress in layers. Someone already mentioned leaving the cotton at home, good advice.
I'm not sure it will be cold enough for you to want the handwarmers, but they're light, I'd go ahead and throw a couple in your pack.
If you will be hiking to a stand/sit down point, I'd reccomend not overdressing in the morning. The hike will warm you up. The last thing you want is to sweat heavily into all your layers and then sit down in the cold.
Put a couple layers in the pack, and dress up when you arrive at where you're sitting.
You are headed to a great area.
Another great firestarter, is cotton balls with vaseline on them. Nice and light and you can put them in a medicine bottle or small tin, even a ziplock.
Good luck. I'm hunting same season, differrent area.