You should tell them how you earn with bitcoin and make them aware about what you've been doing for 6 years is not that simple. The only reason why those parents agreed to teach their kids is they think that you can easily earn from it since you are doing it at the comfort of your home. They should be aware that bitcoin and other cryptocurrencies are not a get rich-quick scheme like how some of the investment schemes portray it.
I think that was a personal matter already so it's not needed and maybe someone can get obsessed with you and plan to do a bad thing once they figured out that you made tons of money already with it. This is why it's still better to be humble and just do your main prospects which is to teach them about btc.
Their parents agree because they know the guy already. Another thing is the lecture is done inside the subdivision so they are sure to be safe. Don't worry the op is not going to tell it, that btc is a quick rich scheme because as you can see in his pic, he started with the basics and then list down what things can we do with a btc.