318 "Rebuild ish"

I see what you're after and I think it's a viable idea. Actually I think it's a great idea. Let the kid get his hands dirty;learn some things; work with his Pops and hopefully be able see ;hear;and enjoy a satisfying result.
Cool!!
A while back I read an article in Hot Rod they did what you are doing with a 318. Took a used but not abused 318 motor and freshened it up. No machine work. Seems like after 60000 miles the engine was still going strong and it became the engine for their 400 hp build.
I personally would change very little. The engine is a system and one change leads to another and another $$$. You know the tune.

As far as camshafts; I'd be inclined to reuse the existing one. Make a tray to hold the lifters and pushrods so they go back in the exact same location.
If changing cams (I'd be suspicious of the cam bearings too) perhaps a factory 340 cam?