As the child ages, the tablet can be switched to different modes. For the toddler, the tablet provides games (e.g. name the object), jigsaws, drawing. The colour be selected from a menu with big "buttons" that the child learns to understand.
For the older child, the tablet can revert to how and adult would use it, with a standard operating system, wifi, browser, learning applications, and games. One toy could last through all stages of development. And it's longevity would justify the cost.