Everyone has to find their own way to Allah.
We cannot simply raise our children according to the Sunnah, try to teach them what is right and wrong, and expect them to love Allah (SWT), Prophet Muhammad (SAW), and Islam just like that. They have to live, make mistakes, and develop their own relationship with Allah, subhaana wa taala.
I sometimes hear people say that they have done everything by the Sunnah but their children aren't religious. This happens a lot by the time they become teenagers and young adults. Well, I want to say to those people, "You haven't wasted a second, insha'Allah!" You gave them the right foundation and the basic background. But, they have to LEARN that what you taught them is right. They have to learn that Islam is the Haqq (truth/reality).
We all had to go through things, whether we are converts or born Muslim. We all did haram things, we all struggled to do better, and, at some stage, many of us fell in love with Islam. We became mu'min (true believers). Islam didn't just make sense, but it made us happy and filled our lives with purpose and joy. Why would we expect it to be any different for our children?
It is a very difficult thing to do, but you have to give your children some space to learn for themselves. It is heartwrenching to see our children, or anyone we love, do anything that displeases Allah (SWT). We want them to avoid Allah's (SWT) anger, His punishment. But try to remember your own journey to Allah. Sometimes, when we take the time to look back at all the mistakes we made, and the time it took us to develop our Islam, it opens our eyes to how much it took to get us where we are. And where are we? Still striving, learning, and making mistakes up to this day!
It has already been decreed by Allah whether your children are destined for Jennah or not and what path they will take in their lives. That is Allah's Qadar (Divine Preordainment).Once they become young adults, the biggest support you can give them is to be a good example, show Islam in every aspect of daily life, be understanding, and pray for them.
Truly success lies only with Allah, subhaana wa taala.