I think casinos can also provide tutorials about using crypto on their sites so that ordinary people can know how to play gambling using crypto.
Nothing wrong with old man to gamble, especially for this case OP say that his uncle is not even newbie at all in gambling.
I'm sure his uncle is experienced enough with gambling and he should have known how to deal with it better than newbies.
Anyway, if the idea to learn crypto gambling comes from himself, it is fine for OP to teach him about crypto gambling but ofc OP also needs to tell his uncle anything related to online casinos that can be something new for his uncle.
he needs guidance as he is new to using crypto in gambling. he can easily get rekt by simple mistake in pressing buttons regarding deposit/withdrawal. there are tons of tutorials already out there when dealing with crypto. but a hands on tutorial is a better one as you can explain more on what to do, not to do and all the things in between. just remind them that if they are not sure about what they are doing, use small amount of money to test first, like if the money will go thru or not.