Just did this for my 5 y/o with a cellular-capable Apple Watch Series 5, so when we go to a theme park soon we can track him if he gets lost and call him if needed. It's $10/mo extra on my AT&T unlimited plan and the watch gets its own phone number that can receive calls like any phone. Highly impressed with this functionality Apple and mobile providers have offered!
Same here, for the same reasons… It has a lot of fun features that I use with my daughter. We can sync our watches and do PTT with the Walkie-talkie app, we exchange voice and gif messages… And we have a lot of parental control over her usage.