This is wise and long overdue. I'm not thrilled by the actual .pdf, but that's OK. I DM games with about 20 elementary and middle school students (youngest is 9 years old), and this is much easier than the most simplistic homebrewed game I run. Sometimes I think we underestimate these kids' ability to pick up some of the more complex rules of the game.
What is difficult for them is reading all the books and knowing how to choose their powers, etc - but if you build their choice of character and follow most of the standard D&D 4e rules, they will do very well, thank you!