My understanding is that Whatsapp can not do this unless the person joins Whatsapp.
My daughter is getting my wife’s hand-me-down phone and we would like her to be able to send texts on it even though it will no longer carry full cell service. In fact, it’s a 2014 model and is going to be unable to be used properly(can not do VoLTE).
Anyway, my daughter believes she can send text-messages on our Ipad using the messaging on there. Our Ipad has no cell service at all. Is she right and if so, does android have an app we can grab that will allow some texting using Wifi?