But than again, JamPlay does have a cool scale library tool (which is great for intermediate-advanced players), the production quality of JamPlay videos is generally higher (the educational value is about the same), and they release more new lessons and mini courses in different genres for intermediate-advanced guitarists, which might make them a better choice if you're an established player.
I have heard how giving you are in so many respects of music schooling and I must say that I am impressed. You remind me of the pure idealism that we had in starting Apple. If I were young, with time, I'd likely offer to join and help you in your endeavours. Keep making people happy, not just in their own learning, but in the example you set for them. 
GuitarTricks.com has courses for beginners, intermediate, and advanced players. It is clear if you have never played guitar you can get started right away on this site. They start with the basic explanations of tuning and holding positions and build into various styles of playing and picking. As usual they work on country and blues first as these are often the easiest for a beginning student.
Of course, this top-down lecturing is all very abstract without examples. Let me give you the worst case scenario. My school talent show, 2008. Two friends of mine performED an ambitious but utterly inappropriate Metallica cover in front of the other students, their parents and the faculty. It was excruciating. Although the solos (presumably the only thing they had bothered to practice) were technically flawless, the whole song was undone by their terrible rhythm. The timing of the song became displaced, the chords were so badly fingered that it was difficult to hear the riff and consequently the whole performance fell apart. They looked like morons. They had sacrificed learning basic rhythm and paid the price. Make sure you don’t do the same.
Then, play the notes again on the first string, but in reverse order: fourth fret to open string. Then go back to the second string, back to third and all the way back to the sixth string where you started, playing the notes in reverse each time. When you’ve completed the cycle you will have played each note on the first through fourth frets on each string and back again.
Playing like a pro? Sorry, but learning which colour button to press does not a guitar player make. If a learner removed the bits after two months and thought he/she could play, they would still have fingers which would need a hard pad to be developed. Watching those vids does not convince me at all.knowing how to press a string is not learnt by pressing a button in my humble opinion
Justin Guitar offers a section dedicated to reference – items that will help you develop as a guitarist. There are reference pages (under the ‘Knowledge’ tab on the top menu) on scales, chords and arpeggios, as well as pages that cover guitar gear, including pedal boards and tone settings. You’ll also find some useful printable PDFs of blank TAB pages, blank chord boxes, blank manuscripts and more.
AGE CAN’T HINDER YOU – Working off of muscle memory and visual assistance, ChordBuddy is designed for players of every age. In fact, ChordBuddy is well-suited for those looking to play guitar with arthritis, offering a pain-free method of playing your favorite song. Utilizing ChordBuddy also allows you to learn the guitar on your own, eliminating the need for long guitar lessons with an instructor, which can result in prolonged joint pain.