If you will check the references I gave you, you should be able to reduce your base weight (complete pack minus food, fuel and water) to where your total pack weight will be under 30 lbs. _with_ the gallon of water. This is especially true since you will have shared gear (instead of one shelter, one stove and one pot per person) and, if you eat at Phantom Ranch, don't need a full 3 days' food. My three-day pack (total pack weight) for backpacking in the high Cascades is 18 lbs. Of course that's with only 1 quart of water, but for the high mountains I need heavier clothing, sleeping bag and shelter than you will in the Grand Canyon.

I went through the lightening-up process two years ago. I had to give up backpacking after a knee injury (now 20 years ago) that left me no longer able carry 40+ lb. packs, but now I can once again go out in the high mountain wilderness for a week at a time, quite comfortably, with 25 lbs. Nearly all the information that enabled me to accomplish this was from this website. I didn't stumble onto Mark Verber's articles until later. He has a lot of info on how you can lighten up with not a lot of money. There is no reason, with the gear currently available, for anyone to carry a 40+ lb. pack unless they're going out unsupported for several weeks, or maybe in the middle of winter. Or my youngest son on a family trip last summer--he carried the gear for his young children (5 and 7) and his wetsuit and surfboard.

I'd pay close attention to the park rangers--they are the ones who have to go down and rescue hundreds of hikers every year, most of whom get in trouble due to carrying insufficient water. Remember also that if you have even a minor emergency, you will need water where you are, not several miles down the trail.
May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey