Right now I want your important advice on how to convince them.
Instead of advising your parents to invest in bitcoin, why don't you find a way to invest in bitcoin yourself? You say you have knowledge about bitcoin, but you have never invested in bitcoin, which proves that you know nothing about bitcoin investment, so giving investment advice to your parents is ridiculous.
In my opinion, the best advice for convincing others is to show positive evidence that you have benefited from it. You should do something to prove to your parents that bitcoin is really an investment that can bring superior profits than gold instead of using empty theories to convince them.