Welcome back.

I have a son who is a drummer and it is the best to jam with him. We play songs together. As your son is just getting started I think I would let him choose the song. Something you can both play. 

Aside from that, I think you just need to define what you want to accomplish for your guitar playing. It might be just learning and playing songs, it might be writing songs, it might be jamming freestyle to tracks or friends. 

I think once you had that sorted you could dig into those areas. I went through Fundamentals, but I didn't know anything when I started. So not sure what to offer here, maybe just skim through them if you think it would help you. 

Good luck