WELCOME don't worry about digesting it all nor being able to be hands on with everything, I've been doing this a long time Racing a Nephew since age 4 mostly while Promoting a track for 16 yrs, other than a few parts using NO GO gauges I could not tech a motor If my life depended on it, your track of choice should have a tech man to reach out to make sure your motor is legal, Rub shoulders with some experienced adult racers at the track most all will help out a kid, BEST thing as DAD you can do is not to push it to quickly and don't get caught up in being all about competitiveness, let it progress as it may and JUST enjoy, of course learn where you can but start with only worrying about the basics you can find all the info you need on this site somewhere, don't be afraid to ask questions on this site as well, You will need to get the Kart set-up for him make sure the seat is mounted properly, then get it scaled with a base line in it they will also set cambers and toe, Get as much Tire info for your track as you can and go from there.
Good Luck !!