I think you shouldn’t say convince. Instead stick to introducing them to Bitcoin. How can you do this? It’s simple and straight forward; tell them what Bitcoin is, explain the whitepaper and its content to them. Show them statistics of Bitcoin adoption and even price increases over the past years, explain the value they could get from delving into it, but also highlight the disadvantages so they don’t think it’s a 100% safe haven.
I think we should emphasize the risks they may encounter when investing in bitcoin instead of focusing too much on the advantages of bitcoin. The fact that we focus too much on explaining the advantages of bitcoin and ignore the risks not only makes them fall into illusion, but can also get us into trouble later if their investments lose money.
In my opinion, the OP shouldn't even be doing this because it's his customer and one disadvantage he would face is that this could affect his business. Instead, tell customers that they can learn about bitcoin on their own because everything about it is easy to find on the internet and is not as complicated as they think.
@OP, these are your customers and they are the ones who bring you income, you really need to make the right decisions.