My kid's about the age people start providing mobile phones, but we haven't decided on providing a mobile phone. I'd still like them to be able to contact us from short distances e.g., from the gym we can see in our apartment complex, from the other end of the beach, at our village shops, in the airport etc.

If I bought two Lily Go T-Deck, would those devices be able to communicate out of the box with maybe a little setup?

I don't have any Meshtastic devices already and there aren't many mapped nodes near me, so I am guessing it would be a bit like text-only walkie talkies that we could build further on?