Dodger: Good luck on next years venture!
I have killed Elk with my 280 Remington calibered Rifle and in fact did so with the wonderful Nosler 140 grain Partitions.
Haven't used the 7x57 to Hunt Elk with to date so won't recommend that - but the 280 Remington with carefully placed 140 grain Nosler Partitions WILL kill Elk.
Again best of luck to you two.
Hold into the wind
VarmintGuy