Be mentally prepared for the undertaking. Stuff will break, you are gonna get separated, you might get stuck somewhere, you are gonna forget something, you are not going to be sleeping like at home, etc.
Get in shape. All of you. You are going to be exerting at an elevation you are not used to so it’s gonna be harder on you all then you are used to
I would imagine you will be looking at longer ranges than you are used to. Bring binoculars. And tripods. Spotting scope would be handy
Plan for adverse weather.
Bring hunting packs. Bring headlamps. Bring some very basic first aid supplies.
Plan for layered clothing. Bring good boots.
Give a lot of thought on how you are gonna get the elk out of where you down him. Once you have him down isn’t the time to do that. I would bring some pack frames with meat shelves and rope.
I wouldn’t rely on having cell coverage.
Get maps and go over it with the members in your party.
Plan for possible couple hundred yard shots.
