Honestly, to learn- I'd start with a .308. Ammo is plentiful, reasonably priced (until you get into handloading) and capable. The key, is practice ...and more practice...you won't burn up a barrel on a .308, and once you develop some skills using a "optimal" setup for your conditions will make it a cakewalk.
I agree with this actually. .308 may not be as pleasant on the shoulder, especially with high BC heavy bullets, but it does have a lot of advantages. Many of which are posted above.
If recoil is an issue for the young ones, you can add a recoil pad and lead weight to the rifle to help.