I might make a suggestion of building the PC with your son.
Im 34 now and was blessed enough to have been taught by my uncle how to build computers when I was about 10 years old. That gave me a crazy passion for technology and I actually now work for him in the tech industry making great money.
Not only do I think in this day and age it is almost a mandatory skill to have, it will also be a crazy bonding experience with your son. My dad couldn't care less about that stuff when I was young so my uncle became my best bud over it.
Now a days, computers are so plug-and-play, you can literally go into it knowing almost 0 and still build something extremely easily.
There is a great site called
https://pcpartpicker.com/ where you can start adding parts to a build and it will tell you if there is any compatibility issues on the fly as you are adding stuff.
So if you read about say a good budget gaming processor and add it then read about a good budget graphics card and you add it, it basically tells you if the parts are compatible.
My .02