How can I get my children / kids to be more effectively in spiritual matters?
Children learn more by watching us than by listening to what we say.
Your "example" .. is a key ingredient to passing down your faith. For example, if you blame others when things go wrong, children may learn to avoid taking responsibility. If you pray as a family when life is difficult, children learn they can go to God with their worries.
Jesus spoke about dealing with our own sins before trying to correct others (Luke 6:41-42). In what areas do you fail to make godly choices, especially around your kids?