First, I have to say that I do have children, so my answer is pure speculation and imagination about what I would do if I had kids.
I think that I would encourage my children (if had any) to read from books initially unless I could find an e-reader that was in my price range that had colour as small children enjoy picture books and bright colours.
Once they started to see the pictures in their own heads, I would encourage them to read from both a kind and a book. Books can be borrowed from the local library (cheaper for parents) but children these days are very tech savvy so I guess it would not be long before they were reading on a kindle, iPad or a mobile device.
Oh how things have changed since I was a little kid!