Since you'll BE climbing...buy a climbing pack. 4lb or less. Many posters here like to portray that they are savvy by recommending really expensive brands. The high value and quality at modest cost of Mountain Hardwear, Black Diamond, Marmot, et al or equivalent will work fine and can be had for substantial discounts from many of the internet sources
You are probably experienced, yes? I'd head up to Adams, Baker, Rainier and the North Cascades to get used to the process of acclimatizing. Take white glove liners, white balaclava and a shemagh, too. A white hat with neck flap (Outdoor Research or equivalent) is worth its weight in platinum.
