2instead, find a way to talk to the parent in a manner that won't get on their nerves, hope you get that?
3The best lesson to give a child at a very young age is how to save money,
1LOL, but the OP is not wrong, though; all he wants is the best future for his cousin. After all, you said it all: one of the best lessons to teach a child is how to save, so that when they grow up, it will help them manage their financial life more effectively. The OP is just seeking people's opinions here, and probably he will act based on the advice he gets from the random comments he gets on this topic.
2About that, and like I said above, OP will act based on the opinion he chooses here, and you are not wrong in advising that he should start by consulting the child's parents first. I completely agree with that opinion of yours. @OP, since he's not your child, if you try to take my first advice without consulting his parents, if they get to find out, they may really not be happy with you, if not for anything, but for not letting them know first.
3You are absolutely correct 💯, mate. The Bible says, "Train up a child in a way that when they are old they will not depart from the part you have taught them." So, if they learn good lessons in their childhood, when they grow up, they will make use of those lessons and probably excel with them if it's so beneficial.