Ehhhh I distinctly remember being around 10 years old, getting a miniature landline phone [1], and dialing 911. Then my parents had to explain to the operator that there was no emergency and how sorry they were. Kids do dumb things.
Can you uninstall the phone app, or whatever Apple calls it? I'm using LineageOS and it looks like I can disable it, though I don't care to try right now.
Plus, it's arguably worth risking accidental 911 calls to allow necessary ones. And landlines have had the same risk for decades.
One of my friends kids (about 5) went through a phase where she was fascinated with calling 911. The iPod Touch became the way to handle this, you could hand her the iPod and know she couldn't dial out. Sure an iPad could work, but this girl had siblings and the parents didn't want to have to buy everybody an ipad.