See, everything is a toy to a six year old. Everything they see, hear or handle shapes their development in some way. Devices like smartphones and tablets have great unique uses, like people in other comments are saying, so I'm not suggesting you ban kids from using them or anything.
But I maintain books have far more physical qualities than any tablet or e-reader. Variety, for starters. Tabs and e-readers all come in some shade of black or gray, they all present a very similar glass texture to the touch, and they only have that new gadget smell for two days. On the other hand, very few books are the same. Moving from a magazine to a hardcover to a paperback may be all the same for you and me, but for a 6 year old is an extremely important feast of sensations that informs her developing mind about the myriad materials and textures and smells the world is made of.
When 'Everything is a toy', there is no real meaning whether it's an ebook, a book, a cutting board... The question is, whether a book allows for anything special, or is removing books 'robs a child of a variety'. I think not. We can't all have every stimulus available for our children. I never experienced snow until I was 30. Some kids never see an ocean. Some live in the city, some in a more rural environment. Some have pets, some don't. Future generations will not live with paper in their household. They will not be robbed of anything.
Keep in mind, this isn't saying ebook readers are suitable for everything. No ebook reader, at the moment, can match a huge, colourfully printed kids book, not to mention their fragility and price isn't suitable for kids. The same goes for feelies, pop-up books, cards with animals, or colours or other such educational toys, and so on. Take those out of the equation, and there are no advantages for print over digital. Actually, there is no advantages for print over anything if those are taken out, since a child will just refer to them as yet another toy.
removing books 'robs a child of a variety'. I think not.
By definition, it does. The issue seems to be whether or not that variety matters. Trouble is, that leads to a discussion about parenting instead of tech :/
One of my toddler's favorite books includes items such as a the wool of a lamb and the texture of an elephant's ears. These are things an ebook cannot reproduce.