Acoustics unless you are spending in the 4 figures almost invariably have ty action so they are much harder to play. Electric with a thin pick is the easiest to start.
10 years ago I would have told you to get a Yamaha Pacifica no question. They have gone to in terms of the construction nowadays.
Look at cheap yamahas, squiers, and epiphones. When you get the guitar look at the 12th fret, thats the one with two dots. Look at the distance between the string and the fretboard. If its half an inch then it is WAAAY too much. A lot of pos guitars will do this because the guitar buzzes if you do not crank down the truss rod.
That is the next thing you do: start fretting notes(put your finger down between each fret and pick the string) the note should play clear. If its muted at certain spots or buzzes especially at the low E, its more than likely a pos. Its going to be a cheap guitar so its not going to be perfect throughout the range but the more guitars you check out the better feel you will have.
Plug the thing in. Strum the guitar and check for hissing, popping, lost signals. Move the switch to various positions and check all of the pickups.
And whoever said an instructor is a waste of time is ing clueless. A decent instructor can have your kid playing songs as soon as he learns E and A. If you want your kid fumbling through trying to learn to read tab on their own and picking up ty picking habits then by all means go that route.
This guy is cool and his youtubes are free:
http://www.justinguitar.com/index.php
Good luck