I attempted to start teaching the kids D&D by beginning with 4th edition as it is current and looks to be combat-focused which will keep them entertained. After 3 sessions I have changed my mind and will be introducing them via the Moldvay Basic Set. Here is why:
1) Grindingly slow - This is due to multiple reasons, among which is my unfamiliarity with the nuances of 4th. It's difficult to teach 3 new players how to play RPG's in general on top of teaching them how to play a rules-heavy edition you have not played before yourself. Plus they only made it through 4 rooms in 3 sessions.
2) Powers - I like the concept, but with new players it quickly turned into a situation where Character = Powers. if it wasn't on the list it did not occur to them to try it. I don't want them to learn to play like that.
3) Starter material - I have no starting 4th edition material other than the core books. No adventures, etc. I could make my own, and I was looking forward to it, but I also like the idea of them sharing some of the same experiences as the earlier generations. I have quite a few basic and 1st ed modules and this will give them some shared experiences and make my prep work a lot easier.
So, we're going with old-school training for the crew. Stay tuned.