If someone else has an old (and/or prepay) sim which can receive texts, you can authenticate whatsapp that way. IRC you can also authenticate with a landline. Install whatsapp using the landline number, wait for SMS authentication to fail, then it should ask to call you. Say yes, and you'll get a call with the authentication code. Et voila.
My nieces and nephews are all young children so i definitely want to encourage/educate them to get off corporate controlled communications channels
Good luck with that, is all I can say. Kids are very susceptible to peer pressure, especially as they enter their teen years. It's only when they're in their late teens that they'll open up again and start becoming more critical.