I made a paper wallet for my son and I deposit a smaller amount of Bitcoins there every month. I kept it in a secret place that only me and another person knows.
You have done a great job for your son's future, You know that Bitcoin will be a great asset in future. Not only that but also Bitcoin has already made a great impact on the virtual monetary world. Already Bitcoin has reached a landmark that almost $7800 USD, That means a lot.
I future, Bitcoin will dominate in the global currency market and Bitcoin will be accepted whole around the world, so If you can save some Bitcoin for the future purpose, it must be a great initiative.