I'm going out with just the 6.5, bought a Cooper and am putting one of the new Steiners on it this week, good luck and no harm in bringing your .06 along to camp! I always take two rifles,
I'm no expert on Elk. I've never even pulled the trigger on one myself but I have been along on three rifle and one ML hunt all of which were successful.
We need to keep in mind that our forefathers killed them with pointy sticks, and bow hunters pile them up to this day.
I know this about them without a doubt, like any other mammal if you punch a hole through their heart/lungs or cut the spine or otherwise interrupt the CNS they die.
Shoot the heck out of that CM and figure out how far you can consistently put it in a 6" circle and call that your max range.
Pick your shot carefully, study elk anatomy and learn how to punch it through the heart by waiting for the broadside shot with the foreleg extended. That way the only thing solid you will hit is maybe a rib before punching the heart.
Look at where the spine is relative to the withers and point of the shoulder, and burn it into memory.
If you look around you can find some pictures online that show their anatomy and if you want to, print one off and take it with you on the hunt.
The 6.5's are the most popular big game rifles in Europe today and dominate even Africa on plains game.
The right bullet in the right spot will get it done. I would not hesitate with either my .264wm or .260 Rem to take the shot on an elk in the right circumstances.
Work at it, take care of the basics, work on your marksmanship between now and then and I have no doubt you can succeed.