Having been in on killing over 75 elk, with rifle, pistol, ML and bow, either pulling the trigger or right beside whoever pulled it ,I feel i can speak with some authority.
First lets get something straight here. I went back and re-read you post and what you are asking here has nothing to do with caliber choice, it has to do with bullet placement. Elk do not "drop" unles a bullet enters the brain, breaks the spinal column or hits close enough to it to shock the central nervous system and cause the muscles in the outer extremities to quit working thereby causing the animal to "drop" , fall or otherwise go tits up. Pick whatever caliber you like and shoot a 5-700 lb animal through the ribs and he will be dead on his feet, but he will still be on his feet for sometime.
Another thing that has not been mentioned here in all this talk of what caliber "drops" elk the best is the fact that you are new to hunting, and planning to take your wife, so BEWARE, killing aint pretty! Animails tend to want to stay alive, and they kick , flop, grunt, bawl, bleed and generally make an ugly mess in the dying process. You had better be sure your wife, and yourself, are ready for this.
Another thing to think about is, what happens after that lovely creature has been relegated to so much dead meat, and how to take care of it . You still have to gut it , quarter it, and carry it to what ever mode of transportation you are useing, then get it home and care for it before it gets to be wrapped in those pretty little packages that you thaw out and cook.
Dont get me wrong.....I am glad to welcome both you and your wife to the hunting fraternity, but i want you to know what you are getting into. AJ