I use the AirTags now, but Apple executives have specifically said they should not be used for tracking kids or pets. They lack some features that the other trackers have.
The most obvious is, as you noted, that they depend on proximity to somebody‘s iPhone in order to work. If your kid takes off in a park or a wooded area, the AirTag probably won’t be much use.
Jiobit and some of the other kid trackers also have a “care team“ option which let you give tracking alerts to other people whether they have an android phone or an iPhone. That’s especially helpful for school teachers, grandparents, and other caregivers who might be watching a child for awhile. There’s nothing comparable for the AirTags right now.
And AirTags don’t give you an exact location until your phone is within range of the tag. Jiobit and other purposebuilt child trackers let you identify the exact location from anywhere, so you can alert teachers or first responders if multiple people are searching for a missing child.
Again, I have the AirTags and like them, they have some really cool features including the vertical space indicator which is great for when your keys fell on the floor and slid under the couch. But they’re just a better match for a different use case than A wandering family member. The one where you yourself are searching for what is probably a stationary item and you are going to physically get close enough with your own iphone to find it.