While I'm online I couldn't help but notice this one!
This one is kind of different though, given the experience level.
I'd recommend sticking with the 30-06 that has already delivered such great success....
UNLESS there is a spiritual thing going on with grand dad, that rifle, and grand son taking it out and getting an elk with it. In that case, given the experience level, I have no comment besides "be even more careful" you want good karma attached to that event, not bad memories.
Like I said, at least the guy has experience, needs to be prepared for a more "archery like" impact on elk compared to what you are used to seeing with the 30-06.