Family trip to Israel?
The birthright trip helps a lot of people connect to their heritage.
I would like to know, if they are acting respectful when they are in the home or in their neighborhood, do they wear a Yarmulka there or not there either. Are they still in touch with friends who are still frum.
Positive role models is very important.
Sometimes people come back after many years. It could be that they miss the warmth of a communuity so the parents should see where the children are holding, are they without any alternative community, if so, they will be lonely, so eventually they might find their way back. One positive thing is that they do know that they can come back to something.