Why would it make you a bad person? You might live to be 90 and you could have 40 good years with your kid. There are young parents who die young as well, so I don’t see how that would be a problem.

Try to get them to switch to Signal if you can. I helped my 70+ year old mother switch with no problems because the UI is similar to WhatsApp and Telegram so it didn’t take her long to get used to it.