iMore:

If you have an old iPhone lying around, chances are you’re not getting much use out of it. I still have my iPhone kicking around here somewhere, but does it ever get turned on anymore? Not when I’ve my trusty iPhone 7 close at hand. But if you have kids, there’s really no need to let a perfectly good device go to waste. They’re probably bugging you to play with your newer iPhone anyway, so give them a device of their own.

Just kid it up first. Here’s how.

My “baby” sister did this for my niece. It’s a great way to re-purpose an old iPhone and gives the child a cool new toy.