If you can swing it (pun intended) I would opt for a few lessons, ask around for someone well recommended. At this age you dont need many, pay attention to what is being taught and why, ask questions, if he has a problem with that then get a different instructor. If your going to be responsible for him you need to learn as well, after a few lessons and some self education you will be able to take over and help him stay the course on the basics until he's a little older. Small steps, dont expect everything all at once.