It does not matter if you are deaf or blind, or suffer from a severe physical disability that limits your movement. Apple devices are the right choice for you, because they were designed with you in mind.
The best iPad for your child is probably the entry level iPad offered by Apple for only $329. You could spend $1,649 for the top-of-the-line iPad with 1 terabyte of storage, but that’s almost certainly not necessary because you can do the same things on both devices.
When comparing the best iPhone with the best iPad available today, the iPhone offers a superior camera by far. However, when considering what the camera for each device is designed for, both the iPhone and iPad offer an excellent camera experience for its intended use.
There are things you can do to prevent your screen from becoming scratched, but placing a screen protector on your new iPad is completely unnecessary. There are better ways to protect and care for your display, without sacrificing the beauty of your iPad.