Chesstempo works for kids !
Help teaching my son

Pandolfini makes good books for kids. He has a decent endgame book that gets pretty sophisticated by the end of it. http://www.amazon.com/Pandolfinis-Endgame-Course-Concepts-Explained/dp/0671656880

Try http://www.chessgym.net/ too; they have simple endings and increase in difficulty. You might like it.
I teach middle schoolers at a school chess club. Regarding the endgame the first video I have them learn is this one:
http://www.youtube.com/watch?v=r3EqM17jvOc

Teach him snf yourself some [mod edit] manners! You run after I busted your ass!
Quoting should you decide to change your post.
[Don't quote such offensive language please. If he changes it before a mod catches it, that's ok. Continued use of the language could get him muted, even banned if he's insistent. Mod.]
Understood.

These are excellent book recommendations. I also recommend that he watches some Ben Finegold lectures, or you could watch them together. I don't want to seem like a Finegold shill but he's a really good teacher, especially with kids.
Lectures call for a a slightly different "style" of learning than tactics puzzles and even books do, so they can help fill in the gaps. It could also help you "organise" the ideas in your head. After watching a lecture you could talk about the ideas with him more in-depth.
As an example, here's a lecture he did on king and pawn endgames.
https://www.youtube.com/watch?v=UnrMMktlpJo
Chess.com is the best place to start. You can try this blog for some real good tips to teach beginners http://kidschessworld.com/level-1/
I am a USCF 1885 and could probably go higher if I played more. However, I did so with almost no study of the endgame. I played a lot of Russian experts and masters in Northern California, so I'm sure the experience rubbed off, and I can calculate. My middle game play, with even decent discipline can be devastating for an A player. And I've used middle game prowess to gain sufficient advantages sometimes even on experts and Masters to get by with a rating of 1885 without any endgame study. I barely know opposition, kid you not lol.
So, now, my dilemma. I am teaching my son. His opening repertoire and middle game play is strong enough that he, at a rating of 454 with 1.75 years of two hours of chess lessons a week.. is now winning regularly against C players in game 15 environments. We practice tactics a LOT.
I want to teach him the endgame. However, unlike the rest of chess, where my talent and play is almost master caliber, my ability to relay concepts in the endgame in actual words is very weak. So, where can I find THIS...
Some source that goes through ideas from beginner on up that you have to know, ideas like opposition, with progressive puzzles WITHOUT making me feel like I'd be teaching 1 + 1 to a 6th grader. Is there an endgame cliff notes out there. Because once I get a short explanation of what I'm teaching, I can fill in all the requisite chess ideas for him.
I'm not looking for a text that is too advanced or that covers too much basic info before moving on to the next topic. I THINK Silman's beginner to master endgame text may be the best I can do, but I'm hoping for better.