A lot of parents struggle with a healthy balance of giving their kid every opportunity to succeed and pushing them too far. A lot of kids would like to have great grades and make their parents proud, but not at the expense of their health and fun. This is why a lot of parents feel guilty about giving their kids Ritalin or Adderall, not to mention the fact that there exists a fair amount of alternatives to Adderall. Even if your children have not been prescribed drugs to help them perform better, you still want to make sure that you help them when possible.
Yet, at a young age their brain is very impressionable and susceptible to long term change. The last thing you want to do is create a dependency on drugs that change brain chemistry at a young age. Most people who get hooked on caffeine at a young age never get off of it, for instance. While caffeine is not the end of the world for most parents, it is the tip of the iceberg if you are opening the smart drug door for kids.
Starting them off early is not a bad idea, but the age should be 18 or older. Having kids change their brain chemistry too much earlier than that is not a good idea and it is useful to speak to a doctor before doing anything. Remember, you have a responsibility to do what is right by them, which is not always what you would do!
While there are few parents who intentionally give nootropics to their children with bad intentions, it is still a problem that you must be aware and vigilant of. Instead of getting them started as soon as you can, just try to make sure you give them a slow and steady introduction to brain improvements through natural means first. Then they can expand their supplementation from there.