There is no practical advise here, do not take this too serious. It's a good entertainment an fun to read some of the comments.
So the he should not get a glow engine - the kid will be overwhelmed with the complicated technology and he will get poisoned
by the fuel.
Electrics are simpler (some believe they are not) , but the Lipo battery and the esc will likely burn and and hurt the kid.
Now you could net a Nimh battery - but they really don't work well in high current applications and probably have a short lifespan.
So maybe a NiCd battery would be the right choice here. They don't perform as well as a Lipo, but be good enough tho get started.
I think everybody has some good and valid points here. It would be more helpful to point out the pros and cons of each setup and be open minded about different opinions. I mean all of us (me, too).
There is simply not a perfect answer for this question.
My suggestion would be - find the nearest club and spend some time talking to the people and watch.
After a while you will have a much better idea on what to get for your boy.
Maybe you find a good deal on a used car.