All of the cartridges you have will take elk nicely,but they are like different golf clubs.Each is a great tool for the correct application.
Each has its advantages and limitations.
Will it be a guided hunt? Or do you have a local you are going with that has hunted this ground?
With good bullets and shot placement,I'd estimate the Whelen and the 7x57 to be good to 250 yds.,maybe a bit more.
With some forms of elk hunting,thats fine.In the 7x57 I'd suggest 150 to 160 gr bullets.I'd also suggest you think in terms of doing surgery on vital organs with the 7x57,and be willing to pass on some shots.It will certainly do through the ribs heart/lung shots.
The Whelen needs no explanation.Within reasonable trajectory it will have the thump and penetration.
If you are going to be working hard,at 7000/8000/9000 feet,you are going tolike a 7 1/2 pound rifle better than a 10pound rifle.
If your contact says it will be longer range shooting,take the 264.Sometimes,by some methods elk hunting CAN be a 400 yd proposal.
Good Luck!! ( having two rifles available is not a bad idea.Where the elk will be is typically contingent on weather.Elk country weather is fickle.
You may not know till near opening day if you will need the 264 or something lighter and handier.