You may want to think about detachable accessory bags that attach to a backpack. Check out REI for pack gear, keep your camera gear in seperate detachables in the front (or other handy place)and an extra belt to clip the bags on for short excursions. I just ordered a couple of bags from Cabela's. One is a carry-on bag, 450ci w/ one main bag and 4 outer zippered compartments, on sale for $9.99. The other one is their Cabela's Delux bag, 950ci of stowage and well padded for $24.95. Both were listed in the "bargain cave" with shipping and tax, together less than $50 total. I'll post pix of them when they show up.
Hope you enjoy the excursion, makes me wish I were going on one.