Normally the internet which is coming in our homes is not filtered and you can access anything on it. Since now internet can be opened on mobile too, its hard to trace the activities of the children on mobile phone. Unfortunately the world we are living in right now, it hard to control children from gambling. Even most gambling sites allow you to play without KYC, so minors can also play and lose money.
Not when you educate them on what to surf and not to surf online, in this age of technology we need to understand that everything are now accessible and there should be limitations on what your children can see online, if they do not follow you, you can always take their phone, I always warn my children about what they are doing online if they failed to follow they know that they will have one week without a phone.