Convincing them to invest in bitcoin for their retirement plan will not work if not supported with real testimonies. At least, you should be profitable with your investment first so that you can easily attract them and make them believe that bitcoin is never a scam but certainly a profitable source of income. That way, once they invest, at least it’s their own decision since the money are theirs and not because of your own will.
Well, we can say that the most convincing power is to show other people the output of your crypto investment first which I agree with that. Maybe, if OP has it, possible his parents will be convinced. But for me, I don't make decisions about what my parents wanted with their money. Let us say that Bitcoin investment is profitable but can't say that all people who invest in this area went well, some ended up losing their money because of being impatient and lack of knowledge about the market. And this will possibly happen to his parents.
