RE: Backpack List....OK??
I have a 4500 and would not recommend getting one smaller than that unless you are a youth or something. The 4500 isn't really all that much space even with good backpacking gear.
Take lots of stuff. You're only doing 2 miles, even though it's a lot of climbing. It sounds like you're going to get there early, so do two trips if you have to. Be prepared. Have a good camp. Don't get too cold.
A Thermarest is invaluable. If you're in the market for one they're awesome. I had a friend get drunk and float the Clark Fork River on his sleep pad last year. He floated through all the rapids, never sank. That convinced me to buy one and I would never go back to cold nights on the ground.
Stick with a filter. Tablets taste terrible and drops have that warning saying if you don't mix the two liquidsright they're both extremely poisonous. It's worth the weight.
My $.02 (might not be worth that)