Do you believe it's a good idea to persuade an elderly person about risky things considering that your senior dad is already 79 years old? What happens if the price of Bitcoin continues to fall? Given his age, are you certain it won't affect his health negatively? When inviting someone to invest in Bitcoin, you need to know what you're doing and whether it's safe for them.
If his dad have got the real understanding about the market then it is ok. In most cases it is quite risky task to make people understand well and they will be on the panic state forever. For this reason if someone request to know about cryptocurrencies I just give them the idea and brief them about the risks associated. In this act it is possible to stay on the safer side, because when they invest and doesn't have patience they'll surely end up losing and the blame will be upon us. This happens when the person lacks understanding about cryptocurrencies.