i am a lot like you are, 3rd gen mechanic and 2nd gen racer, we are new to karting too, little man started at 7yrs and just turned 8, we were in novice & rookie last year and JR1 this year...
the things that helped me/us the most
1) really understanding cross & stagger, getting trough the turns without scrubbing speed, the hardest part for me was tricking him into driving the kart loose, that took a few months of coaching and tweeking
2) if you can mount a go pro on his HEAD or somewhere you can see his HANDS & FEET, was a HUGE HELP
3) i got an ALFANO track timer, it will overlay your laps on a GPS map of the track, then i can show him his fast laps & slow laps and work on his line
4) Teaching him the terms, Loose, Push, Drift, Tight etc, once i could watch his video, and talk to him, i could better explain to him how to tell me the kart is handling... if the crew chief can not get good info from the driver you will never work out the issues.
and MOST IMPORTANTLY 5) HAVE FUN, he is a kid, do not make it about winning, but we all know loosing is not fun too, and they run the risk of loosing interest when they are loosing all the time