Do young kids carry on Shabbos? Do they open and shut lights? Do they play ball on Shabbos? Do you stop a 2 or 3 year old from riding his bike in the backyard on Shabbos? They learn as they grow and as their brains are able to understand more and more. It is up to you as the parent to realize what they are capable of learning and retaining at their level. You can only account for how you raise your children and you can’t account for how someone else does it.
Do you force your 2 year old daughter to wear tights in 90 degrees? At what age do you think that is appropriate? At what age would you stop taking your son in the pool with you? At 4, at 5, at 6? Well there are different opinions among different people. Some would say that they would NOT trust their husband to watch their 4 year old in the pool. Others would say he is in cheider with a Rebbe and does not belong in the pool with women. To me a 4 year old is a baby and belongs with his mommy.