One of the challenges for churches that have great youth/children's programs is getting the involvement of their parents.
There are a few things that can be done here:
1. Visit them: the youth minister or Sunday school superintendent (aka children's minister) visits parents of the attendees, perhaps twice a year.
1a. Invite all the parents of a 'class' or age-group to an afternoon tea, perhaps once a quarter (the Christmas quarter can be a whole class Christmas party).
2. A function is held for parents once a year. This might be a dinner with an after-dinner speaker on some aspect of children' s development.
3. Run a couple of shorter seminars each year on an aspect of children's/young people's spiritual development that parents can participate in: e.g. Bible reading, prayer habits, dealing with their questions.
4. Invite a group of parents to a quarterly meeting to brief them on the ministry and get their views.
5. Issue a quarterly newsletter to parents with some relevant articles, cartoons, etc.
All these create a deeper contact with the parents and for those on the edge of the congregation, might develop some closer fellowship.