Concerning the guitar for your son I'd say look at some beginner's pack. They're not a greatest quality but normally comes with everything you need for a pretty good price. Epiphones makes some good startup packs. They call them value pack sometimes.
Why do I suggest such packs for kids? Honestly, kids tends to want to try out a lot of things. Which is great, that's how they find what they like and what they don't like in life but you can really dig deep into a wallet if you start getting each gear separately. If your son tries it and don't like it then the lost is not too much.