My daughter’s best friend has covid, but they’re able to chat to each other over regular RF walkie talkies. Given they’re both at home, it feels to me like you could sell little units that are connected to the wifi and are keyed to a “server” – it’s essentially just a discord audio channel (or its own). So the kids can talk to each other without requiring a computer or a phone but you get much better fidelity and two way chat (pressing the button is annoying). You could also offer a headphone jack so they could plug in a headset for gaming mode.
If the kids had their own phones they could use discord, but this would reach kids who aren’t allowed their own phone.