Have you seen the Fender x Loog guitars?:
https://www.fender.com/en-US/lifest...ter-3-string-childrens-guitar/9190021088.html
For those who don’t know Loog, it was a Kickstarter to build a 3 string guitar for kids. The idea was to simplify learning guitar, by having less strings to worry about (they can switch to 6 strings later). So, it’s mostly power chords, and simple chords (triads).
Now Fender did a collaboration with Loog, and created a Stratocaster and Telecaster shaped guitars for kids.
Maybe 7 is old enough for a 6 string. But if you see him struggling (specially with barred chords, or handling chords in general) a Loog guitar is a good introductory instrument, in my opinion.