Should be a piece of cake. There are any number of large backpacks that will fit the bill. I looked at Tamrc, Lowepro and Kata before deciding on a Tamrac over the Lowepro natureTrekker AW. My biggest concern was finding one that had good harness for hiking. On a recent trip out west, I used a Tamrac Expedition 7 carrying the following: 2 EOS bodies, 28-135 lens, 12-24 lens, 70-200 f2.8, 1.4x & 2x TCs, Canon S2, 2 chargers, 6 memory cards, 2 extra sets of AAs, maps, powerbars, books and extra clothes. I had it as my airline carry on bag and it just fit into the overhead compartment. I snuck it onto their scale at check in and it came in just shy of 30 lbs. It's worth noting that at that weight the harness wasn't providing as much support as I'd have liked. I didn't bring a laptop but that pocket was great for holding paper - books, magazines, maps etc.
Dan