It sounds to me like the big difference between a "real", laminated board book and a children's book being displayed on an e-ink device is droolability and chewability. Perhaps Kobo should see it as a new need to be filled and make a rugged, chewable (maybe in various flavors), and drool proof child's Kobo reader!
They can 1-up Amazon in this new frontier!
On a serious note, I have a 6 year old and a 4 year old that are very different. The first one was not orally fixated at all. He never used a pacifier. He did chew his crib a couple times while teething. The four year old is opposite. He has and will put about anything in his mouth. Also likes licking windows, car doors, people, dogs, etc. Both had board books and both have read on my Kobo or used the Kobo app on their iPads. Both are working on sight words with the excellent sight word books available in the Kobo store.