Teach them QWERTY. I use Programmer's Dvorak and I love it. But I also have a very specialized setup and everything optimized for myself. Your kids will have to work with different setups in the next decade or two. For them it's more important to be flexible. Later when they specialized themselves and only work in an environment they control they can switch and choose whatever fits them.
To get philosophical, a parents' job is more to prepare a kid for the world as it is, rather than engrain your own preferences to the point of impracticality.
