You got a beauty!!
Cowboyco--In the late '40's to early '60's there was quite a cottage industry, sporterizing and modifying military surplus rifles from WWII. It was cheaper at the time than buying a new Rem or Win, plus you got a one-of-a-kind rifle made just for you.
Both smiths and handymen did this, and the workmanship varied from just absolutely awful to really nice and beautiful.
When I was in college, many moons ago, seriously hacked-up Mausers, Springfields, and Enfields were to be had, used, in every gun shop. If you picked them over carefully you might find one that wasn't quite so bad. And they were almost within financial reach of even a starving college student.
You seem to have gotten hold of one of the well-done upper-end ones, and at a bargain price, too, for today. Even if it is a commercial rather than a military Mauser, my suggestion would be to leave it "as is," especially since it is a good shooter.
Unless the boy is hiking all day with the rifle on a sling, 11# shouldn't be too much of a burden. And the weight will help hold down the recoil, making it easier for him to concentrate on the shot, rather than on the coming smack in his shoulder.
If you--or your boy--insist on a lighter rifle, I'm certain that a collector would be happy to trade you for a similar but lighter Mauser, in a similar caliber, but nowhere near the quality workmanship that you have in this rifle. Or keep this for when your son appreciates it, and for now buy an M1 Carbine for him to use. It'll kill deer at close range, and no one could complain about its weight.
Anyhow, good luck with it, and thanks for sharing!